Mi.50 M2hb Qcb: Infantry Machine Gun

FN HERSTAL

MI.50 M2HB QCB Infantry Machine Gun Calibre .50 (12.7 x 99 mm)

Maintenance manual August 2009 (Change 2) Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

THIS DOCUMENT IS THE PROPERTY OF FN HERSTAL, S.A. IT MAY NOT BE USED, REPRODUCED OR DISCLOSED TO A THIRD PARTY WITHOUT PRIOR FORMAL CONSENT OF FN HERSTAL, S.A.

Maintenance manual

-12009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

NOTES : - The descriptions and illustrations in this maintenance manual may differ slightly from the present configuration of the product. This would reflect the constant evolution of the product during its industrial life. - Data in this manual is technical only and of no contractual value.

TABLE OF CONTENTS CHAPTER 1 : GENERALITIES 1.1. 1.2. 1.3.

1.4. 1.5. 1.6.

Introduction ........................................................................................................ 9 Description ......................................................................................................... 9 Technical data................................................................................................... 10 1.3.1. Dimensions and weight ........................................................................ 10 1.3.2. Functional data ................................................................................... 10 1.3.3. Ballistics .............................................................................................. 11 Accessories ....................................................................................................... 12 Kits .................................................................................................................. 12 Abbreviations .................................................................................................... 13

CHAPTER 2 : IDENTIFICATION OF THE PARTS 2.1. 2.2.

How to order parts ............................................................................................ Parts lists .......................................................................................................... 2.2.1. Barrel group [ 1 ] ................................................................................. 2.2.2. Receiver group [ 2 ] ............................................................................. 2.2.3. Barrel extension group [ 3 ]................................................................... 2.2.4. Feed cover group [ 4 ] .......................................................................... 2.2.5. Bolt group [ 5 ] .................................................................................... 2.2.6. Rear sight group [ 6 ] ........................................................................... 2.2.7. Buffer group [ 7 ] ................................................................................. 2.2.8. Cocking handle group [ 8 ] .................................................................. 2.2.9. Back plate group [ 9 ] ..........................................................................

15 15 17 21 33 37 43 49 53 57 63

CHAPTER 3 : OPERATING PRINCIPLES 3.1. 3.2. 3.3.

Empty machine gun in the initial condition ........................................................... Loading and cocking the machine gun ................................................................ Firing the machine gun ...................................................................................... 3.3.1. The operation of the moving parts ......................................................... 3.3.2. The feeding operation .......................................................................... 3.3.3. The firing operation .............................................................................

69 69 69 71 77 81

Maintenance manual

-22009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 4 : SAFETY INFORMATION 4.1. 4.2.

Warnings and cautions ...................................................................................... 83 Safety checks .................................................................................................... 83

CHAPTER 5 : RECEPTION OF THE GUN ....................................................................................................................... 87

CHAPTER 6 : USING THE MACHINE GUN 6.1. 6.2. 6.3. 6.4.

Preparatory operations ....................................................................................... Loading and cocking the machine gun ................................................................ Firing the machine gun ...................................................................................... Unloading the machine gun ...............................................................................

89 91 93 95

CHAPTER 7 : FIELD STRIPPING 7.1. 7.2.

Disassembling the machine gun ......................................................................... 97 Reassembling the machine gun ........................................................................ 101

CHAPTER 8 : MAINTENANCE 8.1. 8.2. 8.3.

Lubricant specifications .................................................................................... 107 Cleaning and lubrication before firing ............................................................... 109 Cleaning and lubrication after firing .................................................................. 111

CHAPTER 9 : DISASSEMBLY AND REASSEMBLY 9.1.

Barrel group [ 1 ] ............................................................................................ 9.1.1. Removal and reinstallation of the carrying handle assembly (120) .......... 9.1.2. Removal and reinstallation of the carrying handle locking latch (125) ..... 9.1.3. Removal and reinstallation of the carrying handle (123) ........................

119 119 121 121

Maintenance manual

-32009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 9 : DISASSEMBLY AND REASSEMBLY (continued) 9.2.

9.3.

9.4.

Receiver group [ 2 ] ......................................................................................... 123 9.2.1. Removal and reinstallation of the rear cartridge stop assembly (3500) and the front cartridge stop (3828) ...................................................... 123 9.2.2. Disassembling and reassembling the rear cartridge stop assembly (3500) .............................................................................................. 125 9.2.3. Removal and reinstallation of the left and right belt holding pawls (3601) and (3602) ....................................................................................... 127 9.2.4. Removal and reinstallation of the guide screw (3861) and the safety washer (3863) ................................................................................... 129 9.2.5. Removal of the barrel support (3817) and the shim (3818) .................... 131 9.2.6. Reinstallation of the barrel support (3817) and the shim (3818) ............. 133 9.2.7. Removal of the breech bearing (3819) ................................................. 137 9.2.8. Reinstallation of the breech bearing (3819) .......................................... 139 9.2.9. Removal and reinstallation of the locking pin (3821) ............................. 141 9.2.10. Removal of the breech lock cam (3816) and the locking spring (3812)... 143 9.2.11. Reinstallation of the breech lock cam (3816) and the locking spring (3812) .............................................................................................. 143 9.2.12. Removal and reinstallation of the trigger bar (3846) ............................. 145 9.2.13. Removal and reinstallation of the trigger bar stop knurled nut (3651) and the trigger bar stop bracket (3653) ............................................... 145 9.2.14. Removal and reinstallation of the front sight (3824), the front sight cover (3826) and the front sight base (3854) ....................................... 147 9.2.15. Removal and reinstallation of the cover pawl (3831) and its spring (3832) .............................................................................................. 147 9.2.16. Removal/disassembly and reassembly/reinstallation of the bolt latch assembly (B4) .................................................................................... 149 9.2.17. Removal of the extractor switch (3836) and its spring (3837) ................. 151 9.2.18. Reinstallation of the extractor switch (3836) and its spring (3837)........... 153 Barrel extension group [ 3 ] .............................................................................. 155 9.3.1. Removal and reinstallation of the barrel locking spring blade (241) ........ 155 9.3.2. Removal and reinstallation of the breech lock (221) .............................. 157 9.3.3. Marking the barrel extension body (C1) ............................................... 159 Feed cover group [ 4 ] ..................................................................................... 161 9.4.1. Removal and reinstallation of the feed cover (D1) ................................. 161 9.4.2. Removal and reinstallation of the belt feed lever (471) and the belt feed slide assembly (D2) ............................................................................ 163 9.4.3. Disassembling and reassembling the belt feed slide assembly (D2) ......... 165 9.4.4. Removal and reinstallation of the feed cover latch spring (472) .............. 167 9.4.5. Removal and reinstallation of the extractor spring (476) ........................ 167 9.4.6. Removal and reinstallation of the feed cover latch shaft (440) and the feed cover latch (479) ........................................................................ 169

Maintenance manual

-42009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 9 : DISASSEMBLY AND REASSEMBLY (continued) 9.5.

9.6.

9.7.

9.8.

9.9.

Bolt group [ 5 ] ............................................................................................... 9.5.1. Removal and reinstallation of the extractor/ejector assembly (840) ......... 9.5.2. Removal and reinstallation of the bolt switch (831) ............................... 9.5.3. Removal and reinstallation of the cocking lever (865) and its pin (866) ... 9.5.4. Removal and reinstallation of the firing pin spring stop (868) and the lock (867) ......................................................................................... 9.5.5. Removal and reinstallation of the sear slide (864), the sear (863) and its spring (862) .................................................................................. 9.5.6. Removal and reinstallation of the firing pin assembly (E2) ...................... 9.5.7. Disassembling and reassembling the extractor/ejector assembly (840) .... 9.5.8. Disassembling and reassembling the firing pin assembly (E2) ................. 9.5.9. Marking the bolt (820) ....................................................................... Rear sight group [ 6 ] ....................................................................................... 9.6.1. Removal and reinstallation of the rear sight assembly (500) ................... 9.6.2. Removal and reinstallation of the rear sight leaf assembly (520), the rear sight windage knob (541) and the rear sight windage adjusting screw (545) ....................................................................................... 9.6.3. Removal and reinstallation of the rear sight windage scale (547) ............ 9.6.4. Removal and reinstallation of the rear sight base spring (549) ............... 9.6.5. Disassembly and reassembly of the rear sight leaf assembly (520) .......... Buffer group [ 7 ] ............................................................................................ 9.7.1. Removal and reinstallation of the buffer body lock (961) ....................... 9.7.2. Removal and reinstallation of the accelerator (962) .............................. 9.7.3. Removal and reinstallation of the breech lock depressors (912).............. 9.7.4. Disassembly and reassembly of the barrel buffer assembly (920) ............ Cocking handle group [ 8 ] .............................................................................. 9.8.1. Removal of the cocking handle assembly (H1) ...................................... 9.8.2. Reinstallation of the cocking handle assembly (H1) ............................... 9.8.3. Removal and reinstallation of the cocking slide lever (713), the cocking handle (730) and the cocking handle spring (716/1) ............................ 9.8.4. Removal/disassembly and reassembly/reinstallation of the cocking slide assembly (H2).................................................................................... 9.8.5. Removal and reinstallation of the cocking slide stud (726) ..................... 9.8.6 Removal and reinstallation of the cocking slide plunger (721) and its spring (722) ...................................................................................... Back plate group [ 9 ] ...................................................................................... 9.9.1. Removal and reinstallation of a handle grip (632) and its tube (631) ...... 9.9.2. Removal and reinstallation of the buffer tube sleeve (620), the buffer plate (634), the fiber buffer disks (635) and the buffer disks screw (636) ................................................................................................ 9.9.3. Removal and reinstallation of the back plate latch lock (644) and its spring (646) ...................................................................................... 9.9.4. Removal and reinstallation of the back plate latch (648) and its spring (649) ................................................................................................ 9.9.5. Removal/disassembly and reassembly/reinstallation of the safety assembly (660) .................................................................................. 9.9.6. Removal and reinstallation of the bolt latch release (639), the trigger (641) and the springs (643) ................................................................

171 171 171 173 173 175 175 177 179 181 183 183

185 187 187 189 193 193 195 195 197 199 199 201 203 205 207 207 209 209

211 213 213 215 217

Maintenance manual

-52009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 10 : INSPECTION AND ADJUSTMENTS 10.1. 10.2. 10.3. 10.4.

Checking the firing precision ............................................................................ Adjustment of the sights ................................................................................... Checking and gauging the barrel (110) / (110/1) .............................................. Checking and gauging the headspace .............................................................. 10.4.1. Checking and gauging the headspace at the FM/AM level .................... 10.4.2. Checking and gauging the headspace at the GM level ......................... 10.5. Timing adjustment ........................................................................................... 10.5.1. Checking the timing ........................................................................... 10.5.2. Adjustment of the timing ..................................................................... 10.6. Checking the bolt group [ 5 ] ...........................................................................

219 221 223 231 233 237 239 239 241 245

CHAPTER 11 : TROUBLESHOOTING 11.1. The gun does not fire correctly when the trigger (641) is pushed down ................. 246 11.2. Typical problems ............................................................................................. 248 11.3. Removal of a ruptured cartridge case ................................................................ 249

CHAPTER 12 : SPECIAL INTERVENTIONS 12.1. Changing the machine gun from left-hand to right-hand feeding ......................... 12.1.1. Interventions on the bolt group [ 5 ] ..................................................... 12.1.2. Interventions on the feed cover group [ 4 ] ........................................... 12.1.3. Interventions on the feed tray .............................................................. 12.2. Moving the cocking handle assembly (H1) from the right side towards the left side of the machine gun................................................................................... 12.3. Moving the feed cover latch shaft (440) from the left side towards the right side of the machine gun...................................................................................

251 251 251 255 257 263

Maintenance manual

-62009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 13 : KITS 13.1. ‘Anti-aircraft sights’-kit (500/4) ......................................................................... 13.1.1. Technical data ................................................................................... 13.1.2. List of parts ........................................................................................ 13.1.3. Description ........................................................................................ 13.1.4. Preparing the ring sight assembly (1400) and the AA rear sight assembly (1500/1) for use ................................................................................ 13.1.5. Cleaning ........................................................................................... 13.1.6. Disassembly and reassembly of the ring sight assembly (1400) .............. 13.1.7. Disassembly and reassembly of the AA rear sight assembly (1500/1) ...... 13.1.8. Checking and adjusting the firing precision of the machine gun .............

265 265 265 266 267 268 268 271 275

CHAPTER 14 : ACCESSORIES 14.1. 14.2. 14.3. 14.4. 14.5. 14.6.

List of accessories (part I) ................................................................................. List of accessories (part II) ................................................................................ List of accessories (part III) ................................................................................ List of accessories (part IV) ............................................................................... List of accessories (part V) ................................................................................ List of accessories (part VI) ...............................................................................

279 281 283 285 287 289

CHAPTER 15 : TOOLS AND GAUGES 15.1. Tools .............................................................................................................. 15.1.1. Tool kit for the MI.50 M2HB QCB infantry machine gun (1000) and (1000/1) ........................................................................................... 15.1.2. List of separate OREA ......................................................................... 15.1.3. List of UT........................................................................................... 15.2. Gauges .......................................................................................................... 15.2.1. FM/AM tools and gauges kit for the MI.50 M2HB QCB infantry machine gun (1000/2) and (1000/4) .................................................. 15.2.2. GM tools and gauges kit for the MI.50 M2HB QCB infantry machine gun (1000/3) and (1000/5) .................................................. 15.2.3. List of separate gauges .......................................................................

291 291 293 294 297 297 299 301

CHAPTER 16 : NOTES ..................................................................................................................... 303

Maintenance manual

-72009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

Chrome-plated barrel

(°) (*)

Stellited chrome-plated barrel

(°) (*)

Fig. 1 - The 2 versions of the MI.50 M2HB QCB infantry machine gun (°) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, the front sight and its components are replaced by a ring sight assembly (also refer to § 13.1). (*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, the rear sight group is replaced by an appropriate rear sight assembly (also refer to § 13.1).

Maintenance manual

-82009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 1 : GENERALITIES 1.1.

INTRODUCTION This manual is intended for the personnel responsible for the maintenance of the MI.50 M2HB QCB infantry machine gun. The purpose of the manual is to familiarise the personnel with the operation and the maintenance of the gun, to explain the removal, disassembly, repair and/or replacement of the component parts and to supply the appropriate inspection, gauging and adjustment procedures.

1.2.

DESCRIPTION The MI.50 M2HB (Heavy Barrel) QCB (Quick Change Barrel) infantry machine gun is a shortrecoil-operated, automatic weapon firing the .50 (12.7 x 99 mm) ammunition. The MI.50 M2HB QCB infantry machine gun is available in 2 versions with no particular external differencies (Fig. 1) : Barrel Ammunition feeding

Empty cases ejection Links ejection Cocking system Trigger

Back plate

Chrome-plated

Stellited chrome-plated

Left-hand (*)

Left-hand (*)

Disintegrating M2 or M9 link

Disintegrating M2 or M9 link

Downwards

Downwards

To the right (**)

To the right (**)

Manual cocking handle (***)

Manual cocking handle (***)

On the back plate

On the back plate

Provided with a safety

Provided with a safety

Spade grips

Spade grips

(*) The weapon can be changed from left-hand to right-hand feeding by using the corresponding accessory kit. (**) When the weapon has been changed to right-hand feeding, the links are ejected towards the left side. (***) In the standard configuration, the cocking handle is at the right side. If desired, the cocking handle can be moved towards the left side, independently if the weapon is changed to right-hand feeding or not.

Unless specified differently, all paragraphs of this maintenance manual apply to the 2 versions of the MI.50 M2HB QCB.

Maintenance manual

-92009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

1.3.

TECHNICAL DATA

1.3.1.

Dimensions and weight Chrome-plated barrel Overall length

Stellited chrome-plated barrel

1654 mm (65.1“)

Width

228 mm (9.0”)

Height

193 mm (7.6”) (°) ± 38 kg (84 lb)

Weight (empty)

(°) ‘With lowered sights’ in case of a machine gun equipped with the ‘anti-aircraft sights’-kit

1.3.2.

Functional data Operating principle :

By short-recoil of the barrel

Calibre :

.50 (12.7 x 99 mm)

Firing modes :

Single-shot, full-automatic

Barrel length :

1143 mm (45.0”)

Barrel weight :

12 kg (26.46 lb)

Rifled length :

1035 mm (40.7”)

Distance between front and rear sights (*) :

505 mm (19.9”)

Distance between line of sights and barrel bore (*) :

90 mm (3.6”)

Sight setting (*) :

From 0 m to 2500 m : - Rear sight leaf assembly (520) lowered (for quick firing (combat situations, ...)) : Fixed battlesight set for approx. 800 m - Rear sight leaf assembly (520) raised : Adjustable from 200 m to 1200 m in steps of 200 m and from 1200 m to 2500 m in steps of 100 m

Barrel cooling :

By air

Number of grooves :

8

Twist and direction :

381 mm (15.0”) right-hand

Cyclic rate of fire :

450 - 635 rpm

Effective rate of fire :

100 rpm

(*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, refer to § 13.1.1.

The specifications and other figures are given for indication only and have no contractual value. FN HERSTAL S.A. reserves the right to modify or to change the specifications at any time without prior notice.

Maintenance manual

- 10 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

1.3.

TECHNICAL DATA (continued)

1.3.3.

Ballistics .50 (12.7 x 99 mm) calibre ammunition Overall length :

138.43 mm (5.45”)

Muzzle velocity :

916 m/s with M33

Initial kinetic energy :

18,040 J with M33

Effective range :

1,850 m (± 6,000 ft) (depending on the ammunition)

Maximum range :

6,500 m (± 21,000 ft)

Main types of ammunition :

Name

Bullet tip colour (according to the standard STANAG 2953/AOP-2B)

Ammunition type

M33

None

Ball

M17

Red

T (Tracer)

AP-M8

Black

AP (Armour - Piercing)

API-M8

Silver

API (Armour - Piercing - Incendiary)

APT-115

Red and black

APT (Armour - Piercing - Tracer)

APIT-M20

Red and silver

APIT (Armour - Piercing - Incendiary - Tracer)

APEI-169

Silver and yellow

APEI (Armour - Piercing - Explosive - Incendiary)

NOTE : Blank ammunition is also available. When using blank ammunition, the combined recoil booster assembly (also refer to § 14.3), should be installed on the machine gun.

Maintenance manual

- 11 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 1.4.

MI.50 M2HB QCB machine gun

ACCESSORIES Chrome-plated barrel Barrel periscopic inspection device Web barrel cover

Stellited chrome-plated barrel OK

Available in olive-green and sand-yellow

Web weapon cover

Available in sand-yellow

Cordura weapon cover

Available in olive-green

Pair of anti-heat gloves

OK

Flash-hider assembly

OK

Linking and delinking machine

OK

Inversion kit feeding / cocking (left-hand <-> right-hand)

OK

Combined recoil booster assembly

OK

NATO base rear sight assembly + Picatinny support (*)

OK

NATO base AA rear sight assembly + Picatinny support (-)

OK

NATO base AA rear sight assembly + AA rear optical sight (-)

OK

Kit Picatinny rail

OK

(*) Not applicable in case of a machine gun equipped with the ‘anti-aircraft sights’-kit (-) Only applicable in case of a machine gun equipped with the ‘anti-aircraft sights’-kit

OK :

1.5.

Available as accessory for this (these) MI.50 M2HB QCB version(s)

KITS Refer to Anti-aircraft sights

OK :

Chrome-plated barrel

§ 13.1

Stellited chrome-plated barrel OK

Available as kit for this (these) MI.50 M2HB QCB version(s)

Chapters 1 to 12 and 14 to 16 of this maintenance manual have been written for the MI.50 M2HB QCB infantry machine gun without kits. If the presence of a kit on the machine gun has a significant influence on the information contained in these chapters, a special remark and/or a reference towards the appropriate (sub)paragraph of chapter 13 will be made.

Maintenance manual

- 12 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 1.6.

MI.50 M2HB QCB machine gun

ABBREVIATIONS CAT n° : Fig. : ft : g: HB : J: kg : lb : m: mm : m/s : N: OREA : QCB : Qty : rpm : s: UT : “:

Catalog number Figure Feet Gram Heavy Barrel Joule Kilograms Pounds Metres Millimetres Metres/second Newton “Outil de Réparation et d’Entretien Armes” (special tool for weapon repair and maintenance) Quick Change Barrel Quantity Rounds per minute Seconds Universal Tool (commercial tool not considered as a FN Herstal product, but which can be supplied on special request) Inch

NOTE : A vertical line at the left side of a paragraph, an illustration, a table, ... indicates that (a part of) the latter has been changed compared to the previous ‘change’ version.

Maintenance manual

- 13 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

[1]

[8] [4] [6] (°)

(*) [2]

a

[9] [5] [8]

[3]

[7] [5]

a

Fig. 2.a - The 9 main groups of the MI.50 M2HB QCB infantry machine gun

Maintenance manual

- 14 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 2 : IDENTIFICATION OF THE PARTS 2.1.

HOW TO ORDER PARTS For ordering parts, refer to the ‘Catalog of parts and accessories’ of the MI.50 M2HB QCB infantry machine gun.

2.2.

PARTS LISTS The MI.50 M2HB QCB infantry machine gun is subdivided into 9 groups (Fig. 2.a) :

Group Description

Fig.

Paragraph

2.b

2.2.1

2.c.1 2.c.2

2.2.2.1 2.2.2.2

[1]

Barrel group

[2]

Receiver group (part I) Receiver group (part II) (°)

[3]

Barrel extension group

2.d

2.2.3

[4]

Feed cover group

2.e

2.2.4

[5]

Bolt group

2.f

2.2.5

[6]

Rear sight group (*)

2.g

2.2.6

[7]

Buffer group

2.h

2.2.7

[8]

Cocking handle group

2.i

2.2.8

[9]

Back plate group

2.j

2.2.9

(°) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, the front sight (3824), the front sight base (3854) and the front sight cover (3826) are replaced by the ring sight assembly (1400) (also refer to § 13.1). (*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, the rear sight group [ 6 ] is replaced by the rear sight assembly (1500/1) (also refer to § 13.1).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

126

120

123 127

125

121 IV

a

a

II

122 V III I

3817 (Fig. 2.c.1)

3818 (Fig. 2.c.1)

110 (*) 110/1 (**)

b

3100 (Fig. 2.c.1)

b

201 (Fig. 2.d)

Fig. 2.b - Barrel group [ 1 ] Maintenance manual

- 16 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.1.

Barrel group [ 1 ]

MI.50 M2HB QCB machine gun

(a) List of parts (Fig. 2.b) CAT n°

Description

Qty per unit

110 110/1 120 121 122 123 125 126 127

Barrel, chromium plating QCB phos EPR (spare) (*) Barrel, stellite liner QCB phos EPR (spare) (**) Carrying handle assembly > Handle body and rod assembly > Spring type straight pin, slotted > Plastic jacket, barrel carrier assembly > Latch, handle, locking barrel > Plain washer > Nut, hexagonal, self-locking, single slot

1 1 1 1 1 1 1 1 1

(*) Only MI.50 M2HB QCB with chrome-plated barrel (**) Only MI.50 M2HB QCB with stellited chrome-plated barrel

(b) Description The barrel group [ 1 ] of the MI.50 M2HB QCB consists of the barrel (110) / (110/1) onto which the carrying handle assembly (120) has been fitted. The only difference between the 2 versions of the MI.50 M2HB QCB machine gun described in this maintenance manual is the bore of the barrel (110) / (110/1) : • MI.50 M2HB QCB with chrome-plated barrel (marked ‘STD-CHR’) • MI.50 M2HB QCB with stellited chrome-plated barrel (marked ‘CHR-STL’)

The barrel (110) / (110/1) is of the QCB(Quick Change Barrel)-type : it can be removed and installed quickly and easily. The barrel (110) / (110/1) is fitted, through the barrel support (3817) (also refer to § 2.2.2.1) and the front opening of the receiver group [ 2 ], into the barrel extension body (C1) (also refer to § 2.2.3) and then secured into position by turning the carrying handle assembly (120) by 60° towards the left side. In order to ensure that the rear end of the barrel (110) / (110/1) fits correctly into the front opening of the barrel extension body (C1), the barrel has a slot (I) which should be aligned with the inner protruding extremity of the guide screw (3861) inside the barrel support (3817) (also refer to § 2.2.2.1) when the barrel is installed. As a result, the 3 series of outer guides on the rear end of the barrel engage the corresponding recesses provided in the front opening of the barrel extension body. In order to ensure that the barrel (110) / (110/1) can only be installed in one longitudinal position, its rear end has a special shape. Note that the correct alignment of the barrel (110) / (110/1) occurs automatically when the barrel group [ 1 ] is held by the carrying handle assembly (120) when installing it. When the barrel (110) / (110/1) is correctly installed, and in order to hold back its rotational movement, the lug on the front end of the barrel locking spring blade (241) (also refer to § 2.2.3) engages the corresponding notch provided in the rear end of the barrel.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

126

120

123 127

125

121 IV

a

a

II

122 V III I

3817 (Fig. 2.c.1)

3818 (Fig. 2.c.1)

110 (*) 110/1 (**)

b

3100 (Fig. 2.c.1)

b

201 (Fig. 2.d)

Fig. 2.b - Barrel group [ 1 ] Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.1.

Barrel group [ 1 ] (continued)

MI.50 M2HB QCB machine gun

(b) Description (continued) The carrying handle assembly (120) is fitted, from the front side, onto the shoulder approximately at the middle of the barrel (110) / (110/1) and it consists of the carrying handle body (121) onto which the following components have been installed : - The carrying handle (123) which is secured to the stem of the carrying handle body (121) by means of the nut (127) used in combination with the washer (126) - The carrying handle locking latch (125) which is secured by and can pivot around the spring pin (122) When the carrying handle assembly (120) is fitted into position, its rear lug (II) should engage the notch (III) provided in the barrel (110) / (110/1). When the rear lug (II) correctly engages the notch (III), the wider part (IV) of the carrying handle locking latch (125) engages the groove (V) of the barrel (110) / (110/1) so that the carrying handle assembly (120) is locked into position. The carrying handle locking latch (125) (and therefore also the carrying handle assembly (120)) can simply be released by manually raising the upper end of the latch until its wider part (IV) is disengaged from the groove (V).

NOTE : It is strongly recommended that, if possible, the carrying handle assembly (120) is at all times installed on the barrel (110) / (110/1) because the position of the carrying handle assembly allows to see easily if the barrel group [ 1 ] has correctly been locked into position. The barrel group [ 1 ] is correctly locked into position when the carrying handle assembly (120) has been turned by 60° towards the left side. If the carrying handle assembly (120) is still in the vertical position, the carrying handle (123) interferes with the line of sights of the machine gun indicating the shooter that the barrel group [ 1 ] has not been locked into position.

Maintenance manual

- 19 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

3818/7 3818/8 3818/9 3818/10 3818/11 3818/12

3818/1 3818/2 3818/3 3818/4 3818/5 3818/6

3861 3863 B

3000

3505

3817 3834

3828

e

B

d

B2

l

f

c

A e

3504

d

3503

3820 3502

f c

3835

3500

h

SY

YY

Y

3819 3834 j i j g

3821

l

3835 k

3813

3822

b

k

a

3823 i

B1 3816

3603

a

3601

3100

3602 g

3600

3812 3827

h

All the parts represented on Fig. 2.c.2 are also part of the complete receiver 3000

b

3815 3814

Fig. 2.c.1 - Receiver group [ 2 ] (part I) The serial number of the machine gun (required when marking the barrel extension body (C1) (also refer to § 9.3.3) or the bolt (820) (also refer to § 9.5.9)) has been marked in the front part of the upper rear plate of the receiver frame (B1) (also refer to ‘SYYYY’ in the above diagram).

Maintenance manual

- 20 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.2.

Receiver group [ 2 ]

MI.50 M2HB QCB machine gun

2.2.2.1. Receiver group [ 2 ] (part I) (a) List of parts (Fig. 2.c.1) CAT n° 3000 3100 3812 3813 3814 3815 3816 3819 3820 3500 3502 3503 3504 3505 3600 3601 3602 3603 3817 3818/1 3818/2 3818/3 3818/4 3818/5 3818/6 3818/7 3818/8 3818/9 3818/10 3818/11 3818/12 3821 3822 3823 3827 3828 3834

Description

Qty per unit

Complete receiver MK2 (for quick change) > Receiver, proved > > Spring, locking > > Screw, breech lock cam > > Nut, locking cam > > Split pin > > Cam, breech lock, receiver assembly > > Bearing, breech thread > > Screw, lock, breech, bearing > Stop, assembly, cartridge, rear > > Pawl, aligning, cartridge > > Plunger, cartridge aligning pawl > > Spring, cartridge > > Pin, straight, headless > Pawl, assembly, belt holding > > Pawl, belt holding, left-hand > > Pawl, belt holding, right-hand > > Sleeve, belt holding pawl > Support barrel > Shim, trunnion block 1 > Shim, trunnion block 2 > Shim, trunnion block 3 > Shim, trunnion block 4 > Shim, trunnion block 5 > Shim, trunnion block 6 > Shim, trunnion block 7 > Shim, trunnion block 8 > Shim, trunnion block 9 > Shim, trunnion block 10 > Shim, trunnion block 11 > Shim, trunnion block 12 > Pin, locking, trunnion block > Spring, trunnion block lock > Split pin > Spring, pawl > Stop, front, cartridge > Pin, locking

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 2

Maintenance manual

- 21 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

3818/7 3818/8 3818/9 3818/10 3818/11 3818/12

3818/1 3818/2 3818/3 3818/4 3818/5 3818/6

3861 3863 B

3000

3505

3817 3834

3828

e

B

d

B2

l

f

c

A e

3504

d

3503

3820 3502

f c

3835

3500

h

SY

YY

Y

3819 3834 j i j g

3821

l

3835 k

3813

3822

b

k

a

3823 i

B1 3816

3603

a

3601

3100

3602 g

3600

3812 3827

h

All the parts represented on Fig. 2.c.2 are also part of the complete receiver 3000

b

3815 3814

Fig. 2.c.1 - Receiver group [ 2 ] (part I) The serial number of the machine gun (required when marking the barrel extension body (C1) (also refer to § 9.3.3) or the bolt (820) (also refer to § 9.5.9)) has been marked in the front part of the upper rear plate of the receiver frame (B1) (also refer to ‘SYYYY’ in the above diagram).

Maintenance manual

- 22 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.2.

Receiver group [ 2 ] (continued)

2.2.2.1. Receiver group [ 2 ] (part I) (continued) (a) List of parts (continued) CAT n°

Description

Qty per unit

3835 3861 3863

> Pin, belt holding pawl > Screw, guide, barrel quick change MK2 > Safety washer, screw and plug > Also refer to § 2.2.2.2

2 1 1

The following parts or assemblies cannot be ordered (separately) : a number has however been attributed in order to facilitate the descriptions throughout this maintenance manual :

N°

Description

B1 B2

Receiver frame Rear cartridge stop

Qty per unit 1 1

(b) Description The receiver group [ 2 ] (catalog number (3000), also called ‘complete receiver’) consists of the receiver (3100) onto or into which the following assemblies and components have been installed : - The assemblies and components represented on Fig. 2.c.2 and described in § 2.2.2.2. - The rear cartridge stop assembly (3500) and the front cartridge stop (3828), mounted onto the right side of the ammunition feeding and ejection section of the receiver (3100) The rear cartridge stop assembly (3500) and the front cartridge stop (3828) are held in place by a mounting pin (3835) which, on its turn, is secured by means of a locking pin (3834). The rear cartridge stop assembly (3500) consists of the rear cartridge stop (B2) which is used to retain the corresponding link when the cartridge is extracted from the ammunition belt and which has been provided with the cartridge aligning pawl (3502). The cartridge aligning pawl (3502), used in combination with the front cartridge stop (3828), ensures that the cartridge is positioned so that its rim can correctly be engaged by the extractor/ejector assembly (840) (also refer to § 2.2.5). The cartridge aligning pawl (3502) is secured by and can pivot around the pin (3505) and is held in a spring-tensioned position by means of its spring (3504) used in combination with the corresponding plunger (3503). Please note that this configuration corresponds to the standard case of a left-hand fed MI.50 M2HB QCB machine gun : if the gun is converted to right-hand feeding (also refer to § 12.1), the front cartridge stop (3828) will be kept and installed at the left side while the rear cartridge stop assembly (3500) will be replaced, also at the left side, by the link stripper (3829) and the rear cartridge stop (3830), both supplied in the optional accessory kit (8997/2).

Maintenance manual

- 23 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

3818/7 3818/8 3818/9 3818/10 3818/11 3818/12

3818/1 3818/2 3818/3 3818/4 3818/5 3818/6

3861 3863 B

3000

3505

3817 3834

3828

e

B

d

B2

l

f

c

A e

3504

d

3503

3820 3502

f c

3835

3500

h

SY

YY

Y

3819 3834 j i j g

3821

l

3835 k

3813

3822

b

k

a

3823 i

B1 3816

3603

a

3601

3100

3602 g

3600

3812 3827

h

All the parts represented on Fig. 2.c.2 are also part of the complete receiver 3000

b

3815 3814

Fig. 2.c.1 - Receiver group [ 2 ] (part I) The serial number of the machine gun (required when marking the barrel extension body (C1) (also refer to § 9.3.3) or the bolt (820) (also refer to § 9.5.9)) has been marked in the front part of the upper rear plate of the receiver frame (B1) (also refer to ‘SYYYY’ in the above diagram).

Maintenance manual

- 24 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.2.

Receiver group [ 2 ] (continued)

2.2.2.1. Receiver group [ 2 ] (part I) (continued) (b) Description (continued) - The belt holding pawls assembly (3600), mounted onto the left side of the ammunition feeding and ejection section of the receiver (3100) and contributing to the correct feeding of the ammunition belt The belt holding pawls assembly (3600) is held in place by a mounting pin (3835) which, on its turn, is secured by means of a locking pin (3834). The belt holding pawls assembly (3600) consists of the left and right belt holding pawls (3601) and (3602), held together by their (hollow) sleeve (3603). The left and right belt holding pawls (3601) and (3602) can pivot on the mounting pin (3835) and each pawl is held in a spring-tensioned position by means of a pawl spring (3827). Please note that this configuration corresponds to the standard case of a left-hand fed MI.50 M2HB QCB machine gun : if the gun is converted to right-hand feeding (also refer to § 12.1), the belt holding pawls assembly (3600) will be installed at the right side.

- The barrel support (3817) which is screwed, together with a shim (3818/1-12), onto the thread of the trunnion block at the front side of the receiver (3100) and which has been provided with 2 threaded holes for the guide screw (3861) The guide screw (3861), fitted into the upper threaded hole of the barrel support (3817) and used in combination with the safety washer (3863), ensures that the rear end of the barrel (110) / (110/1) is correctly guided through the barrel support towards the front opening of the barrel extension body (C1) (also refer to § 2.2.1 and § 2.2.3). The correct vertical position of the barrel support (3817) and the shim (3818/1-12) is ensured by the locking pin (3821) : the front end of the locking pin fits into the small lower hole (A) of the shim and engages one of the 2 grooves (B) at the rear side of the barrel support. The locking pin (3821) itself fits, from the front side, into its hole in the lower front side of the receiver (3100), is held in a spring-tensioned position by means of the locking spring (3822) and is secured by means of the split pin (3823). For more information about the choice of the correct shim (3818), refer to § 9.2.6.

The receiver (3100) consists of the receiver frame (B1) onto which the following components have been installed : - The breech bearing (3819) which is screwed into the threaded cylindrical mounting support at the front side of the receiver frame (B1) and which is held in place by means of its locking screw (3820) - The breech lock cam (3816), fitted into its housing in the bottom of the receiver frame (B1) and used to guide the breech lock (221/13-28) (also refer to § 2.2.3) The breech lock cam (3816) is fixed by the screw (3813) used in combination with the locking spring (3812) and the nut (3814) : in order to ensure its correct operation, there should be a clearance of 0.05 - 0.20 mm between the breech lock cam and the bottom plate of the receiver frame (B1) (also refer to § 9.2.11). In order to avoid loosening due to vibrations, the nut (3814) is secured to the screw (3813) by means of the split pin (3815).

Maintenance manual

- 25 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

B4 3845

3841

3843 d

d

3842

3844 3826

3839

e

(°)

e

3840

c

3838

b

(°)

3824

(°)

3854

III 3654

3832

c

3836

3831

f a

3837 II

510 (Fig. 2.g)

I f

3100 (Fig. 2.c.1)

3653

b

3833 3825

a

3651

3849

B5

3700

3846

All the parts represented on this Fig. 2.c.2 are also part of the complete receiver 3000 (also refer to Fig. 2.c.1)

Fig. 2.c.2 - Receiver group [ 2 ] (part II) Maintenance manual

- 26 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.2.

Receiver group [ 2 ] (continued)

2.2.2.2. Receiver group [ 2 ] (part II) (a) List of parts (Fig. 2.c.2) CAT n° 3000 3651 3653 3654 3700 3824 3825 3826 3831 3832 3833 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3849 3854

Description

Qty per unit

Complete receiver MK2 (for quick change) (refer to § 2.2.2.1) > Nut, plain, knurled > Bracket, stop, adjustable trigger bar > Screw, externally relieved body > Pin, assembly, trigger lever > Sight, front (°) > Spring type straight pin, slotted > Cover, front sight (°) > Pawl, cover detent > Spring, cover lock > Nut, rear cam, extractor > Switch, extractor > Spring, extractor, switch > Latch, bolt > Rod, bolt latch > Pin, bolt latch rod > Plunger, bolt latch > Spring, plunger, bolt latch > Spring, bolt latch rod > Nut, bolt latch rod > Split pin > Bar, trigger > Spring, safety, extractor cam nut > Base, front sight (°)

1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

The following parts or assemblies cannot be ordered (separately) : a number has however been attributed in order to facilitate the descriptions throughout this maintenance manual :

N°

Description

Qty per unit

B4 B5

Bolt latch assembly Trigger bar stop assembly

1 1

(°) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, the front sight (3824), the front sight base (3854) and the front sight cover (3826) are replaced by the ring sight assembly (1400) (also refer to § 13.1).

Maintenance manual

- 27 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

B4 3845

3841

3843 d

d

3842

3844 3826

3839

e

(°)

e

3840

c

3838

b

(°)

3824

(°)

3854

III 3654

3832

c

3836

3831

f a

3837 II

510 (Fig. 2.g)

I f

3100 (Fig. 2.c.1)

3653

b

3833 3825

a

3651

3849

B5

3700

3846

All the parts represented on this Fig. 2.c.2 are also part of the complete receiver 3000 (also refer to Fig. 2.c.1)

Fig. 2.c.2 - Receiver group [ 2 ] (part II) Maintenance manual

- 28 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.2.

Receiver group [ 2 ] (continued)

2.2.2.2. Receiver group [ 2 ] (part II) (continued) (b) Description The receiver group [ 2 ] (catalog number (3000), also called ‘complete receiver’) consists of the receiver (3100) (also refer to § 2.2.2.1) onto or into which the following assemblies and components have been installed : - The assemblies and components represented on Fig. 2.c.1 and described in § 2.2.2.1. - The trigger bar stop assembly (B5) consisting of the trigger bar stop bracket (3653) onto which the trigger bar stop knurled nut (3651) has been screwed The trigger bar stop assembly (B5) is fixed to the inner upper rear part of the receiver (3100) by means of the screw (3654) which is also used to secure the rear end of the rear sight base (510) (also refer to § 2.2.6). The trigger bar stop knurled nut (3651) determines the upper limit position of the rear end of the trigger bar (3846) which, on its turn, determines the timing of the machine gun. The correct position of the knurled nut is therefore determined by carrying out the timing adjustment described in § 10.5. Once it has been adjusted correctly, the trigger bar stop knurled nut (3651) is held in place by the engagement of the screw (3654) into one of its notches (also refer to § 10.5).

- The trigger bar (3846) which is secured by and can pivot around its pin (3700) The trigger bar (3846) is used to transmit the movement of the trigger (641) (also refer to § 2.2.9) towards the sear (863) which controls the operation of the firing pin (861) (also refer to § 2.2.5). As described above, the upper limit position of the rear end of the trigger bar (3846), which determines the timing of the machine gun, is adjusted by positioning the trigger bar stop knurled nut (3651) as described in § 10.5.

- The front sight (3824) which is screwed into the front sight base (3854) and which is protected by means of the front sight cover (3826) The front sight base (3854) fits into the central groove at the upper front side of the receiver (3100) while the front sight cover (3826) fits into the 2 outer grooves. Both the front sight base (3854) and the front sight cover (3826) are secured by means of the 2 spring pins (3825). The upper hole in the front sight cover (3826) allows adjusting the front sight (3824) without having to remove the cover. In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, the front sight (3824), the front sight base (3854) and the front sight cover (3826) are replaced by the ring sight assembly (1400) (also refer to § 13.1).

- The cover pawl (3831) and its spring (3832) fitted, from the rear side, into their housing underneath the front sight The cover pawl (3831), held in a spring-tensioned position by its spring (3832), ensures that the feed cover (D1) is correctly held at its closed and opened positions.

Maintenance manual

- 29 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

B4 3845

3841

3843 d

d

3842

3844 3826

3839

e

(°)

e

3840

c

3838

b

(°)

3824

(°)

3854

III 3654

3832

c

3836

3831

f a

3837 II

510 (Fig. 2.g)

I f

3100 (Fig. 2.c.1)

3653

b

3833 3825

a

3651

3849

B5

3700

3846

All the parts represented on this Fig. 2.c.2 are also part of the complete receiver 3000 (also refer to Fig. 2.c.1)

Fig. 2.c.2 - Receiver group [ 2 ] (part II) Maintenance manual

- 30 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.2.

Receiver group [ 2 ] (continued)

2.2.2.2. Receiver group [ 2 ] (part II) (continued) (b) Description (continued) - The extractor switch (3836), provided on the inner side of the left side plate of the receiver (3100) and used, in combination with the extractor spring (476) and the extractor guide cam in the feed cover (D1) and with the special cam riveted to the inner side of the left side plate of the receiver, to guide the front end of the extractor/ejector assembly (840) (also refer to § 2.2.4 and § 2.2.5) The extractor switch (3836) is secured by means of the nut (3833) which is screwed, at the left outer side of the receiver (3100), onto the pin of the switch. In order to avoid loosening due to vibrations, the nut (3833) is secured to the pin of the extractor switch (3836) by means of the safety spring (3849). The extractor switch (3836) is held at its raised position by means of its spring (3837) which engages the special groove provided in the inner side of the left side plate of the receiver (3100). The little curved extremity (I) of the extractor switch spring (3837) fits into the hole provided in the groove for the spring while the other extremity of the spring is located under the shoulder (II) of the extractor switch (3836).

- The bolt latch assembly (B4), which is used to hold the bolt (820) back at its rear position at the end of its rearward movement The main components of the bolt latch assembly (B4) are the bolt latch rod (3839) and the bolt latch (3838) itself, held together by the pin (3840) onto which the bolt latch can pivot. After having received the bolt latch rod spring (3843), the front part of the bolt latch rod (3839) is inserted, from the rear side, into the bolt latch mounting bracket (III) provided inside the receiver (3100). Using the assembling tool OREA 558 (also refer to § 9.2.16), the bolt latch rod (3839) is then pushed forwards, against the force of its spring (3843), until its front end protrudes from the front side of the bolt latch mounting bracket (III). The front end of the bolt latch rod (3839) is then finally secured by means of the bolt latch rod nut (3844) which, on its turn, is secured to the rod by the split pin (3845). The bolt latch plunger (3841) and its spring (3842), provided into their housing on top of the bolt latch (3838), exert a downward pressure on the bolt latch when the plunger comes into contact with the inner upper part of the receiver (3100). As long as the bolt latch release (639) is raised, the bolt latch (3838) can freely pivot downwards so that it engages and holds back the bolt (820) when the latter reaches the end of its rearward movement : this situation occurs when the machine gun is set for single-shot firing. When the bolt latch release (639) is locked at its lowered position or simply pushed downwards, the downward pivoting movement of the bolt latch (3838) is restricted by the front end of the bolt latch release. As a result, the bolt latch (3838) is not able to engage and hold back the bolt (820) : this situation occurs when the machine gun is set for automatic firing.

Maintenance manual

- 31 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

110 110/1 (Fig. 2.b)

3817 (Fig. 2.c.1)

3818 (Fig. 2.c.1)

c

3100 (Fig. 2.c.1)

200 ZZ

241 C1

a

221/13 221/14 221/15 221/16 221/17 221/18

c

201

221/19 221/20 221/21 221/22 221/23

221/24 221/25 221/26 221/27 221/28

a YY YY

b

230 b

233

962 (Fig. 2.h)

Barrel extension body (C1) represented upside down

Fig. 2.d - Barrel extension group [ 3 ] The barrel extension assembly (200) may never be interchanged between different machine guns : it must always be used with the same gun (and especially with the same bolt assembly (810)) ! For that reason, the bottom of the barrel extension body (C1) has been marked with the last four digits of the serial number of the machine gun (also refer to ‘YYYY’ on the upside down representation in the lower left corner of the above diagram) (for more information, also refer to § 7.2 and to § 9.3.3). The number of the breech lock (221) (required when marking the bolt (820) (also refer to § 9.5.9) has been marked in its cavity (also refer to ‘ZZ’ in the above diagram).

Maintenance manual

- 32 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.3.

Barrel extension group [ 3 ]

MI.50 M2HB QCB machine gun

(a) List of parts (Fig. 2.d) CAT n°

Description

Qty per unit

200 201 241 221/13 221/14 221/15 221/16 221/17 221/18 221/19 221/20 221/21 221/22 221/23 221/24 221/25 221/26 221/27 221/28 230 233

Barrel extension, MK2 QCB assembly > Extension, barrel QCB, shank and locking spring > > Spring blade, locking barrel > Lock 13, breech (A=14.77+/-0.01) > Lock 14, breech (A=14.81+/-0.01) > Lock 15, breech (A=14.85+/-0.01) > Lock 16, breech (A=14.89+/-0.01) > Lock 17, breech (A=14.93+/-0.01) > Lock 18, breech (A=14.97+/-0.01) > Lock 19, breech (A=15.01+/-0.01) > Lock 20, breech (A=15.05+/-0.01) > Lock 21, breech (A=15.09+/-0.01) > Lock 22, breech (A=15.13+/-0.01) > Lock 23, breech (A=15.17+/-0.01) > Lock 24, breech (A=15.21+/-0.01) > Lock 25, breech (A=15.25+/-0.01) > Lock 26, breech (A=15.29+/-0.01) > Lock 27, breech (A=15.33+/-0.01) > Lock 28, breech (A=15.37+/-0.01) > Pin assembly, breech lock > Spring type straight pin, slotted

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

The following parts or assemblies cannot be ordered (separately) : a number has however been attributed in order to facilitate the descriptions throughout this maintenance manual :

N°

Description

C1

Barrel extension body

Qty per unit 1

Maintenance manual

- 33 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

110 110/1 (Fig. 2.b)

3817 (Fig. 2.c.1)

3818 (Fig. 2.c.1)

c

3100 (Fig. 2.c.1)

200 ZZ

241 C1

a

221/13 221/14 221/15 221/16 221/17 221/18

c

201

221/19 221/20 221/21 221/22 221/23

221/24 221/25 221/26 221/27 221/28

a YY YY

b

230 b

233

962 (Fig. 2.h)

Barrel extension body (C1) represented upside down

Fig. 2.d - Barrel extension group [ 3 ] The barrel extension assembly (200) may never be interchanged between different machine guns : it must always be used with the same gun (and especially with the same bolt assembly (810)) ! For that reason, the bottom of the barrel extension body (C1) has been marked with the last four digits of the serial number of the machine gun (also refer to ‘YYYY’ on the upside down representation in the lower left corner of the above diagram) (for more information, also refer to § 7.2 and to § 9.3.3). The number of the breech lock (221) (required when marking the bolt (820) (also refer to § 9.5.9) has been marked in its cavity (also refer to ‘ZZ’ in the above diagram).

Maintenance manual

- 34 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.3.

Barrel extension group [ 3 ] (continued) (b) Description The barrel extension group [ 3 ] (catalog number (200)) forms the link between the barrel group [ 1 ] and the buffer group [ 7 ]. The front opening of the barrel extension body (C1) has been especially designed to accept the rear end of the QCB-type barrel (110) / (110/1). The correct installation of the barrel (110) / (110/1) is ensured by the engagement of the 3 series of outer guides on its rear end into the corresponding inner guides in the front opening of the barrel extension body (C1). The rear shank of the barrel extension body (C1) ensures the correct connection with the buffer group [ 7 ] (also refer to § 2.2.7). The narrower part of the rear shank fits between and is engaged by the 2 claws of the accelerator (962) while the rear nose of the shank engages the front nose of the buffer piston rod (930).

In addition, the barrel extension group [ 3 ] has been provided with the guides for the back-and-forth movement of the bolt group [ 5 ]. The barrel extension group [ 3 ] consists of the barrel extension body assembly (201) provided with a breech lock (221/13-28). The breech lock (221/13-28) is inserted into the corresponding housing at the rear side of the barrel extension body assembly (201) and is secured in a position allowing a restricted vertical movement by means of the breech lock pin (230). On its turn, the breech lock pin (230) is held in place in the breech lock (221/13-28) by means of the spring pin (233), inserted from underneath. For more information about the choice of the correct breech lock (221), refer to ‘10.4. Checking and gauging the headspace’.

The barrel extension body assembly (201) consists of the barrel extension body (C1) with, on its right side, the barrel locking spring blade (241). The barrel locking spring blade (241) is fitted, from the front side, into its housing in the right side of the barrel extension body (C1) and then held into position by staking. The lug on the front end of the barrel locking spring blade (241) engages the corresponding notch in the rear end of the barrel (110) / (110/1) when the latter is correctly locked into position.

Maintenance manual

- 35 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

f

410

481

VI

c

IX

g

b

484

III V b d

II

a

a

476

479

IV 472

c

I 450

475

XI VII e

440

474 VIII

478

460

471

D1

X

430

477

D2

d

482 473

e

h

f

483 g

400

h

3100 (Fig. 2.c.1)

Fig. 2.e - Feed cover group [ 4 ] Maintenance manual

- 36 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.4.

Feed cover group [ 4 ]

MI.50 M2HB QCB machine gun

(a) List of parts (Fig. 2.e) CAT n° 400 410 430 440 450 460 471 472 473 474 475 476 477 478 479 481 482 483 484

Description

Qty per unit

Cover group assembly (for latch to the left) > Cover assembly > Pawl assembly, belt feed, upper > Shaft assembly, cover catch > Slide, belt feed > Pin assembly, belt feed pawl > Lever, belt feed > Spring, cover latch > Spring, lock, retaining, belt feed lever > Spring, helical, compression > Pin, feed lever > Spring, cover, extractor > Arm, belt feed pawl > Spring, pawl assembly > Latch, cover > Washer, shaft, cover latch > Pin, cover axis > Split pin > Split pin

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

The following parts or assemblies cannot be ordered (separately) : a number has however been attributed in order to facilitate the descriptions throughout this maintenance manual :

N°

Description

D1 D2

Feed cover Belt feed slide assembly

Qty per unit 1 1

(b) Description The feed cover group [ 4 ] (catalog number (400)) is used to feed the ammunition belt, from the left side, into the receiver (3100). Please note that the links are ejected out of the right side of the receiver (3100) and that the empty cases leave the gun through the ejection opening in the bottom of the receiver. Also note that this corresponds to the standard case of a left-hand fed MI.50 M2HB QCB machine gun : if the gun is converted to right-hand feeding (also refer to § 12.1), the ammunition belt is fed from the right side and the links are ejected out of the left side of the receiver (3100).

Maintenance manual

- 37 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

f

410

481

VI

c

IX

g

b

484

III V b d

II

a

a

476

479

IV 472

c

I 450

475

XI VII e

440

474 VIII

478

460

471

D1

X

430

477

D2

d

482 473

e

h

f

483 g

400

h

3100 (Fig. 2.c.1)

Fig. 2.e - Feed cover group [ 4 ] Maintenance manual

- 38 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.4.

Feed cover group [ 4 ] (continued) (b) Description (continued) The feed cover group [ 4 ] consists of the feed cover (D1), secured to the receiver (3100) by means of the feed cover axis pin (482) which, on its turn, is secured by means of the split pin (483). The feed cover (D1) consists of the feed cover body (410) into which the following assemblies and components have been provided : - The feed cover latch (479) which is held in a spring-tensioned position by means of its spring (472) and which can be actuated by using the feed cover latch shaft (440) The feed cover latch (479) ensures that the feed cover (D1) remains correctly locked into position when it is closed. On the other hand, the latch releases the closed feed cover when the feed cover latch shaft (440) is turned. The feed cover latch shaft (440) is fitted into the feed cover body (410) from the left side and the right end of the shaft is secured by means of the split pin (484) used in combination with the washer (481). The feed cover latch shaft (440) has been provided with a slightly protruding central lug (I) which engages the notch (II) of the hole in the feed cover latch (479). The feed cover latch spring (472) is fitted, with the wider end of its elongated hole, onto the small rear mounting pin (III) of the feed cover body (410) and then pushed as far as possible rearwards. The feed cover latch spring (472) is oriented so that its front claw (IV) faces the feed cover body (410). The feed cover latch spring (472) is positioned correctly when its front claw (IV) engages the corresponding groove in the feed cover body (410) and when the pointed front part (V) of the feed cover latch (479) fits between the rear end of the spring and the feed cover body. Please note that this corresponds to the standard case of a left-hand mounted feed cover latch shaft (440) : if its handle has been provided at the right side of the machine gun (also refer to § 12.3), the shaft is fitted into the feed cover body (410) from the right side.

- The extractor spring (476) used, in combination with the extractor switch (3836) on the inner side of the left side plate of the receiver (3100), with the special cam riveted to the inner side of the left side plate of the receiver and with the extractor guide cam (part of the feed cover body (410)), to guide the front end of the extractor/ejector assembly (840) (also refer to § 2.2.2.2 and § 2.2.5) The extractor spring (476) is fitted with its front end onto the small front mounting pin (VI) of the feed cover body (410) while the lug (VII) on the rear end of the spring fits into the notch in the extractor guide cam.

Maintenance manual

- 39 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

f

410

481

VI

c

IX

g

b

484

III V b d

II

a

a

476

479

IV 472

c

I 450

475

XI VII e

440

474 VIII

478

460

471

D1

X

430

477

D2

d

482 473

e

h

f

483 g

400

h

3100 (Fig. 2.c.1)

Fig. 2.e - Feed cover group [ 4 ] Maintenance manual

- 40 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.4.

Feed cover group [ 4 ] (continued) (b) Description (continued) - The belt feed slide assembly (D2) which is used, in combination with the belt holding pawls assembly (3600) (also refer to § 2.2.2.1), to push the ammunition belt into the machine gun The belt feed slide assembly (D2) consists of the belt feed slide (450) onto which the assembly formed by the belt feed pawl (430) and the belt feed pawl arm (477) has been mounted. The belt feed pawl arm (477) is fitted onto the rear side of the belt feed pawl (430) with its free extremity (VIII) pointing towards the right side. The assembly formed by the belt feed pawl (430) and the belt feed pawl arm (477) is secured to the left side of the belt feed slide (450) by means of the pin (460) and is held in its raised position by means of the pawl spring (478). The belt feed slide assembly (D2), which is engaged and actuated by the front end of the belt feed lever (471), carries out a to-and-fro motion in its housing in the front part of the feed cover body (410). Please note that this configuration corresponds to the standard case of a left-hand fed MI.50 M2HB QCB machine gun : if the gun is converted to right-hand feeding (also refer to § 12.1), the belt feed slide assembly (D2) is assembled and oriented differently. For more information about the operation of the belt feed slide assembly (D2), refer to § 3.3.2.

- The belt feed lever (471) which converts the back and forth movement of the moving parts into a to-and-fro motion of the belt feed slide assembly (D2) The belt feed lever (471) can pivot on the (larger) right mounting pin (IX) of the feed cover body (410) and is fixed to the mounting pin by means of the retaining spring (473). The rear end (X) of the belt feed lever (471) engages the appropriate groove on top of the bolt assembly (810) (also refer to § 2.2.5) while the front end of the lever fits into the notch (XI) at the rear side of the belt feed slide assembly (D2). The belt feed lever (471) is held in a spring-tensioned position by means of its pin (475) and the spring (474) which fit into the rear housing in the lever, just behind its pivoting point. Please note that this configuration corresponds to the standard case of a left-hand fed MI.50 M2HB QCB machine gun : if the gun is converted to right-hand feeding (also refer to § 12.1), the belt feed lever pin (475) and the spring (474) will be fitted into the front housing in the belt feed lever (471), just in front of its pivoting point.

Maintenance manual

- 41 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

870

831 865 863 823

c

e d

840

III II

V YY YYZZ

867

844

L

R

862

f

VII 843

IV

E1

e

d

VI

864

f

868

842

VIII c

I

820 E2

866

a

853

850

861 852 b b a

E3

810 800

Fig. 2.f - Bolt group [ 5 ] The bolt assembly (810) may never be interchanged between different machine guns : it must always be used with the same gun (and especially with the same barrel extension assembly (200)) ! For that reason, the upper front part of the bolt (820) has been marked with the last four digits of the serial number of the machine gun as well as the number of the presently used breech lock (221) (also refer to ‘YYYY-ZZ’ in the above diagram) (for more information, also refer to § 7.2 and to § 9.5.9).

Maintenance manual

- 42 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.5.

Bolt group [ 5 ]

MI.50 M2HB QCB machine gun

(a) List of parts (Fig. 2.f) CAT n° 800 810 820 823 831 840 842 843 844 850 852 853 861 862 863 864 865 866 867 868 870

Description

Qty per unit

Bolt n°2 group > Bolt n°2 complete group > > Bolt 2 > > > Pin, shoulder headless > > Switch, bolt alternate feed > > Extractor, cartridge, assembly > > > Ejector > > > Spring, ejector, compression > > > Pin, ejector, grooved, headed > > Extension, assembly firing pin > > > Spring, pin firing > > > Pin, retaining firing pin > > Pin, firing > > Spring, sear compression > > Sear > > Slide, sear > > Lever, cocking > > Pin, cocking lever > > Lock, accelerator stop > > Stop, spring, firing pin > Rod assembly, driving spring

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

The following parts or assemblies cannot be ordered (separately) : a number has however been attributed in order to facilitate the descriptions throughout this maintenance manual :

N°

Description

Qty per unit

E1 E2 E3

Extractor Firing pin assembly Firing pin extension body

1 1 1

Maintenance manual

- 43 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

870

831 865 863 823

c

e d

840

III II

V YY YYZZ

867

844

L

R

862

f

VII 843

IV

E1

e

d

VI

864

f

868

842

VIII c

I

820 E2

866

a

853

850

861 852 b b a

E3

810 800

Fig. 2.f - Bolt group [ 5 ] The bolt assembly (810) may never be interchanged between different machine guns : it must always be used with the same gun (and especially with the same barrel extension assembly (200)) ! For that reason, the upper front part of the bolt (820) has been marked with the last four digits of the serial number of the machine gun as well as the number of the presently used breech lock (221) (also refer to ‘YYYY-ZZ’ in the above diagram) (for more information, also refer to § 7.2 and to § 9.5.9).

Maintenance manual

- 44 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.5.

Bolt group [ 5 ] (continued)

MI.50 M2HB QCB machine gun

(b) Description The bolt group [ 5 ] (catalog number (800)) controls the cartridge feeding, extraction and ejection operations as well as the operation of the firing pin (861) and consists of the bolt assembly (810) and the driving spring assembly (870). For more information about the operation of the bolt group [ 5 ] and its different components, refer to chapter 3.

The bolt assembly (810) consists of the bolt (820) (including the pin (823)) onto or into which the following assemblies and components have been installed : - The extractor/ejector assembly (840) which fits, with its hinge pin, into its housing in the left side of the bolt (820) The extractor/ejector assembly (840) consists of the extractor (E1) and the ejector (842). The ejector (842), held in a spring-tensioned position by means of its spring (843), is secured to the front end of the extractor (E1) by means of the pin (844). The front end of the extractor/ejector assembly (840) is guided by the extractor switch (3836) (provided on the inner side of the left side plate of the receiver (3100) (also refer to § 2.2.2.2)), by a special cam riveted to the inner side of the left side plate of the receiver and by the extractor spring (476) and the extractor guide cam in the feed cover (D1) (also refer to § 2.2.4).

- The bolt switch (831) which fits, from above, into its opening in the bolt (820) The bolt switch (831) is used to complete the appropriate groove for the rear end of the belt feed lever (471) (also refer to § 2.2.4) on top of the bolt assembly (810). In the standard case of a left-hand fed MI.50 M2HB QCB machine gun, the groove of the bolt switch (831) should face the inscription ‘L’ on the upper side of the bolt (820) in order to obtain a continuous groove. In case of a right-hand fed MI.50 M2HB QCB machine gun, the groove of the bolt switch (831) should face the inscription ‘R’ on the upper side of the bolt (820) in order to obtain a continuous groove. The correct positioning of the bolt switch (831) is ensured by the pin (823) (part of the bolt (820)) which engages the corresponding hole in the bolt switch. The bolt switch (831) itself is held in place in the bolt (820) by the hinge pin of the extractor/ ejector assembly (840).

- The firing pin assembly (E2) which fits, from the rear side, into its housing in the bolt (820) and which is held back by the sear (863) The firing pin assembly (E2) consists of the firing pin (861) fitted onto the front end of the firing pin extension (850). The firing pin extension (850) consists of the firing pin extension body (E3) into which the firing pin spring (852) has been fitted and secured by means of the pin (853).

Maintenance manual

- 45 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

870

831 865 863 823

c

e d

840

III II

V YY YYZZ

867

844

L

R

862

f

VII 843

IV

E1

e

d

VI

864

f

868

842

VIII c

I

820 E2

866

a

853

850

861 852 b b a

E3

810 800

Fig. 2.f - Bolt group [ 5 ] The bolt assembly (810) may never be interchanged between different machine guns : it must always be used with the same gun (and especially with the same barrel extension assembly (200)) ! For that reason, the upper front part of the bolt (820) has been marked with the last four digits of the serial number of the machine gun as well as the number of the presently used breech lock (221) (also refer to ‘YYYY-ZZ’ in the above diagram) (for more information, also refer to § 7.2 and to § 9.5.9).

Maintenance manual

- 46 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.5.

Bolt group [ 5 ] (continued)

MI.50 M2HB QCB machine gun

(b) Description (continued) - The sear (863) which fits, together with its spring (862) and from above, into its housing in the rear part of the bolt (820) The sear (863) is held in its raised position by means of its spring (862) and is secured by the engagement of the notch (I) of the sear slide (864) onto its lug (II). The sear (863), which is pushed down by the front end of the trigger bar (3846) (also refer to § 2.2.2.2) when the trigger (641) (also refer to § 2.2.9) is pushed down, is used to hold the firing pin assembly (E2) back at its cocked position and to release it for the firing operation.

- The cocking lever (865) and its pin (866) The cocking lever (865) fits into position in its housing provided in the upper rear part of the bolt (820) and is secured by and can pivot around its pin (866). The cocking lever pin (866) is inserted, from the left side, into its hole in the bolt (820) and through the hole in the cocking lever (865). The position of the cocking lever (865), which is used to push the firing pin assembly (E2) into its cocked position, is determined by the engagement of its tip into the recess provided in the inner upper rear part of the receiver (3100).

- The firing pin spring stop (868) which fits, from underneath, into the bolt (820) and which is secured by the lock (867) The firing pin spring stop (868) is used to hold back the rear end of the firing pin spring (852) when the firing pin assembly (E2) is cocked. The lock (867) secures the firing pin spring stop (868) into position by the engagement of its fork-shaped front end (III) onto the recess (IV) in the upper end of the stop.

Besides the housings, grooves and holes described above, the bolt (820) has also been provided with the following ones : - The T-slot (V) on its front face for holding the cartridge and extracting the cartridge case - The firing pin hole (not visible on Fig. 2.f) in its front face which allows the firing pin (861) to reach the primer of the cartridge - The engagement groove (VI) in its upper rear part for the engagement of the bolt latch (3838) when the bolt (820) is at its rear position - The housing (VII) for the driving spring assembly (870) in its rear upper right part - The holes (VIII) (on the left and right sides) for the bolt stud (725) (also refer to § 2.2.8) in its lower rear part

Maintenance manual

- 47 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

520

e

523

528

I

529

e

525

d

II 526

524

d

527

522

548 a

545

521

c

551

547

b

546

a

510

542

3654 (Fig. 2.c.2)

b

543

c

541

544 549 500

3100 (Fig. 2.c.1)

3653 (Fig. 2.c.2)

Fig. 2.g - Rear sight group [ 6 ] (*) Maintenance manual

- 48 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.6.

Rear sight group [ 6 ] (*)

MI.50 M2HB QCB machine gun

(a) List of parts (Fig. 2.g) CAT n° 500 510 520 521 522 523 524 525 526 527 528 529 541 542 543 544 545 546 547 548 549 551

Description

Qty per unit

Sight assembly, rear (meters) > Base assembly, rear sight > Leaf assembly, rear sight > > Leaf, rear sight 3 > > Slide, rear sight > > Knob, elevating screw > > Screw, elevating, rear sight slide > > Pin rear sight, elevating knob > > Pin, retainer, rear sight, elevating screw > > Nut, half, rear sight > > Plunger, elevating, rear sight > > Spring, plunger, elevating, rear sight > Knob, rear sight, windage screw > Pin, knob, windage screw > Plunger, rear sight, windage click > Spring, windage click > Adjusting screw, windage, rear sight > Stop, rear sight leaf > Scale, windage, rear sight > Screw, scale, rear sight > Spring, rear sight base > Screw, sight base

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 2

(b) Description The rear sight group [ 6 ] (catalog number (500)) has been provided on the upper rear part of the receiver (3100). The front part of the rear sight group [ 6 ] is secured by the 2 screws (551) which are part of the rear sight group. The rear part of the rear sight group [ 6 ] is fixed by the separate screw (3654) which is also used to secure the trigger bar stop assembly (B5) to the inner upper rear part of the receiver (3100) (also refer to § 2.2.2.2). The bottom of the rear sight group [ 6 ] has been provided with 2 positioning pins which engage the corresponding holes in the upper plate of the receiver (3100).

(*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, the rear sight group [ 6 ] is replaced by the rear sight assembly (1500/1) (also refer to § 13.1).

Maintenance manual

- 49 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

520

e

523

528

I

529

e

525

d

II 526

524

d

527

522

548 a

545

521

c

551

547

b

546

a

510

542

3654 (Fig. 2.c.2)

b

543

c

541

544 549 500

3100 (Fig. 2.c.1)

3653 (Fig. 2.c.2)

Fig. 2.g - Rear sight group [ 6 ] (*) Maintenance manual

- 50 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.6.

Rear sight group [ 6 ] (*) (continued) (b) Description (continued) The rear sight assembly (500) consists of the rear sight base (510) onto which the following assemblies and components have been installed : - The rear sight leaf assembly (520) which is secured by and can pivot on the rear sight windage adjusting screw (545) The rear sight leaf assembly (520) consists of the rear sight leaf (521) with a graduated rectangular opening into which the rear sight slide (522) is fitted. The rear sight slide (522) is secured into the rectangular opening of the rear sight leaf (521) by means of the rear sight half nut (527) which is inserted into both the rear sight leaf and the slide from the right side. The teeth on the right side of the rear sight half nut (527) engage the thread of the rear sight slide elevating screw (524) so that the half nut, and therefore also the rear sight slide (522), move along the graduated rectangular opening when the screw is turned. The rear sight slide elevating screw (524) fits into its housing in the right part of the rear sight leaf (521) and is held into position by the pin (526) which engages the recess (I) in the screw. The rear sight slide elevating screw (524) can be turned by using the rear sight slide elevating knob (523) which is fixed to the screw by means of the pin (525) and which is used in combination with the elevating plunger (528) and its spring (529). The elevating plunger (528) and its spring (529), fitted into their housing (II) in the top of the rear sight leaf (521), allow a precise positioning of the rear sight slide elevating knob (523) by generating a click each time the knob is rotated by 60°. The rear sight windage adjusting screw (545) is screwed, from the right side, through the rear sight leaf stop (546), the rear sight base (510) and the rear sight leaf assembly (520). The lateral position of the rear sight leaf assembly (520) can be modified by turning the rear sight windage adjusting screw (545) by using the rear sight windage knob (541). This knob is fixed to the left end of the screw by means of the pin (542) and is used in combination with the windage click plunger (543) and its spring (544). The windage click plunger (543) and its spring (544), fitted into their housing in the rear sight windage knob (541), allow a precise positioning of the knob by generating a click each time the knob is rotated by 90°. For more information about the positioning of the rear sight leaf assembly (520), refer to § 6.1.

- The rear sight windage scale (547) which is fixed to the rear sight base (510) by means of the 2 screws (548) - The rear sight base spring (549) which ensures that the rear sight leaf assembly (520) is correctly maintained at its lowered and raised positions - The 2 screws (551) which are used to secure the front part of the rear sight base (510) to the upper rear part of the receiver (3100) (see above)

Maintenance manual

- 51 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

201 (Fig. 2.d)

913

912 b

c

910

b

962

a

G1 c

961

a

912

950

940 963

G2 d

930

922 d

921 925 920

924

900

Fig. 2.h - Buffer group [ 7 ] Maintenance manual

- 52 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.7.

Buffer group [ 7 ]

MI.50 M2HB QCB machine gun

(a) List of parts (Fig. 2.h) CAT n° 900 910 912 913 961 920 921 922 924 925 930 940 963 950 962

Description

Qty per unit

Body, oil buffer > Body, barrel buffer, assembly > > Depressor, breech lock > > Rivet, solid, depressors > > Lock, buffer body > Buffer, barrel, assembly n°3 > > Tube, barrel buffer > > Split pin > > Head, buffer piston > > Cap, buffer tube > > Rod, oil buffer piston > > Guide, buffer spring assembly > > Spring, guide, buffer > Pin assembly, accelerator > Accelerator, buffer

1 1 2 2 1 1 1 1 1 1 1 1 1 1 1

The following parts or assemblies cannot be ordered (separately) : a number has however been attributed in order to facilitate the descriptions throughout this maintenance manual :

N°

Description

G1 G2

Buffer body Buffer piston assembly

Qty per unit 1 1

(b) Description The buffer group [ 7 ] (catalog number (900)) is located behind the barrel extension group [ 3 ] and absorbs the recoil energy of the barrel (110) / (110/1) and the barrel extension group during their rearward movement. The accelerator (962) and the buffer piston rod (930) ensure the correct locking with the barrel extension group [ 3 ] (also refer to § 2.2.3). The front nose of the buffer piston rod (930) engages the rear nose of the rear shank of the barrel extension body (C1). At the end of the rearward movement, the 2 claws of the accelerator (962) engage the narrower part of the rear shank of the barrel extension body (C1).

Maintenance manual

- 53 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

201 (Fig. 2.d)

913

912 b

c

910

b

962

a

G1 c

961

a

912

950

940 963

G2 d

930

922 d

921 925 920

924

900

Fig. 2.h - Buffer group [ 7 ] Maintenance manual

- 54 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.7.

Buffer group [ 7 ] (continued)

MI.50 M2HB QCB machine gun

(b) Description (continued) The buffer group (900) consists of the buffer body assembly (910) onto or into which the following assemblies and components have been installed : - The barrel buffer assembly (920) which has been inserted, from the rear side, into the hollow rear part of the buffer body assembly (910) The barrel buffer assembly (920) consists of the buffer piston assembly (G2), the barrel buffer tube (921), the buffer spring guide (940) and the buffer spring (963). The buffer piston assembly (G2) consists of the buffer piston rod (930) provided, on its rear end, with the buffer tube cap (925) and the buffer piston head (924). The buffer tube cap (925) is just fitted (without screwing) onto the rear end of the buffer piston rod (930) while the buffer piston head (924) is screwed onto it and secured by means of the split pin (922). A special piston head checking gauge (1682) has been provided to determine the correct position of the buffer piston head (924) on the buffer piston rod (930) (also refer to § 9.7.4). The rear end of the buffer piston assembly (G2) is screwed, by the buffer tube cap (925), into the barrel buffer tube (921). The buffer spring (963) is fitted onto the front end of the buffer piston assembly (G2) and held in place by means of the buffer spring guide (940) which is held back by the protruding pins at the front end of the buffer piston rod (930).

- The accelerator (962) which is secured by and can pivot around its pin (950) The accelerator (962) fits between the breech lock depressors (912) at the front side of the buffer body assembly (910).

The buffer body assembly (910) consists of the buffer body (G1) onto which the following components have been installed : - The 2 breech lock depressors (912) which have been fixed by means of the 2 rivets (913) When, at the beginning of the rearward movement of the moving parts, the left and right extremities of the breech lock pin (230) (also refer to § 2.2.3) come into contact with the inclined face of the front extremity of the corresponding breech lock depressor (912), the pin, and therefore also the breech lock (221) itself, will be pushed downwards.

- The buffer body lock (961) The buffer body lock (961) is fitted, from the rear side, into its housing in the right side of the buffer body (G1). The rear end of the buffer body lock (961) slightly protrudes towards the right side and is used to hold back the moving parts once they have been inserted into the receiver (3100).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

c g

735

723 g

722 a

726

730

719

728

b

721

d

719

717

c

717

713

717

II

719 715

716/1

728 III

711

e

700

727

f

735

H2 724 712 d

714 I H1

a

3100 (Fig. 2.c.1)

718

e

f

b

725

Fig. 2.i - Cocking handle group [ 8 ] Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.8.

Cocking handle group [ 8 ]

MI.50 M2HB QCB machine gun

(a) List of parts (Fig. 2.i) CAT n°

Description

Qty per unit

700 711 712 713 714 715 716/1 717 718 719 721 722 723 724 725 726 727 728 730 735

Slide assembly, retracting (spring to RH) > Bracket, retracting slide > Slide, retracting > Lever, retracting slide > Stud, lever, retracting slide > Washer, retracting slide lever stud > Spring, helical torsion > Nut, stud, shoulder bolt > Bolt, shoulder, bracket, retracting slide > Split pin > Plunger, retracting slide > Spring, plunger, retracting slide > Pin, plunger, retracting slide > Pin, stop, retracting slide > Stud, bolt > Stud, retracting slide > Screw, retracting slide bracket (short) > Screw, retracting slide bracket (long) > Handle, retracting slide assembly > Wire

1 1 1 1 1 1 1 3 2 3 1 1 1 1 1 1 1 2 1 2

The following parts or assemblies cannot be ordered (separately) : a number has however been attributed in order to facilitate the descriptions throughout this maintenance manual :

N°

Description

Qty per unit

H1 H2

Cocking handle assembly Cocking slide assembly

1 1

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

c g

735

723 g

722 a

726

730

719

728

b

721

d

719

717

c

717

713

717

II

719 715

716/1

728 III

711

e

700

727

f

735

H2 724 712 d

714 I H1

a

3100 (Fig. 2.c.1)

718

e

f

b

725

Fig. 2.i - Cocking handle group [ 8 ] Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.8.

Cocking handle group [ 8 ] (continued) (b) Description Please note that the configuration described and illustrated in this paragraph corresponds to the standard case of a right-hand mounted cocking handle group [ 8 ] : the differences resulting from the installation of the group at the left side of the machine gun (also refer to § 12.2), will be mentioned when necessary.

The cocking handle group [ 8 ] (catalog number (700)) allows pulling the moving parts manually towards their rear position. The cocking handle group [ 8 ] consists of the cocking handle assembly (H1), the bolt stud (725) and the components required to fix the cocking handle assembly onto the right (standard configuration) or left side of the receiver (3100). The bolt stud (725) fits into the right (standard configuration) or left hole in the lower rear part of the bolt (820) (also refer to § 2.2.5) and is engaged by the notch (I) on the rear end of the cocking slide (712) when the cocking handle (730) is pulled rearwards. The cocking handle assembly (H1) is fixed to the receiver (3100) by means of the 2 shoulder bolts (718), the screw (727) and the 2 screws (728). The 2 shoulder bolts (718) are installed from the inside of the receiver (3100) and each shoulder bolt is secured by a nut (717) which, on its turn, is secured to the outer extremity of the bolt by means of a split pin (719). The screw (727) (used at the lower rear side) is slightly shorter than the 2 screws (728). The 2 rear screws (the screw (727) and one of the screws (728)) are secured by one of the wires (735). The other wire (735) is used to secure the remaining screw (728) and the cocking slide stud (726).

NOTE : In case of a left-hand mounted cocking handle group [ 8 ], the same cocking slide bracket (711) is used, but the bracket is turned upside down in order to allow its correct installation on the left side of the receiver (3100) (also refer to § 12.2). The cocking handle assembly (H1) consists of the cocking slide bracket (711) onto which the following assemblies and components have been installed : - The cocking slide assembly (H2) which is fitted between the cocking slide bracket (711) and the receiver (3100) and which slides along the slot in the bracket The cocking slide assembly (H2) consists of the cocking slide (712) onto which the cocking slide stop pin (724) and the cocking slide lever stud (714) have been screwed. The cocking slide stop pin (724) has been provided to accept the loop (II) of the cocking handle spring (716/1) / (716/2) and to stop the forward movement of the cocking slide lever (713). The cocking slide lever stud (714) is used for the installation of the cocking handle spring (716/1) / (716/2) and the assembly formed by the cocking slide lever (713) and the cocking handle (730).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

c g

735

723 g

722 a

726

730

719

728

b

721

d

719

717

c

717

713

717

II

719 715

716/1

728 III

711

e

700

727

f

735

H2 724 712 d

714 I H1

a

3100 (Fig. 2.c.1)

718

e

f

b

725

Fig. 2.i - Cocking handle group [ 8 ] Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.8.

Cocking handle group [ 8 ] (continued) (b) Description (continued) - The assembly formed by the cocking slide lever (713) and the cocking handle (730) The assembly formed by the cocking slide lever (713) and the cocking handle (730) is mounted, together with the cocking handle spring (716/1) and the washer (715), onto the outer end of the cocking slide lever stud (714). The assembly is secured by a nut (717) which, on its turn, is secured to the outer extremity of the cocking slide lever stud (714) by means of a split pin (719). The cocking handle spring (716/1) is installed between the cocking slide lever (713) and the shoulder of the cocking slide lever stud (714). The loop (II) of the cocking handle spring (716/1) fits onto the cocking slide stop pin (724) while the bent extremity (III) of the spring fits into a small hole provided in the cocking slide lever (713). Please note that, in case of a left-hand mounted cocking handle group [ 8 ] (also refer to § 12.2), the cocking handle (730) is mounted on the other side of the cocking slide lever (713) while the cocking handle spring (716/1) is replaced by the cocking handle spring (716/2).

- The cocking slide stud (726) which is screwed into the lower front threaded hole of the cocking slide bracket (711) The cocking slide stud (726) is used as a support in order to facilitate the initiation of the pivoting movement of the cocking slide lever (713) when the cocking handle (730) is pulled rearwards. The cocking slide lever (713) is forced back forwards by the cocking handle spring (716/1) / (716/2). As described above, the cocking slide stud (726) is secured, together with the closest screw (728), by means of one of the wires (735).

- The cocking slide plunger (721) and its spring (722) The cocking slide plunger (721) and its spring (722) fit, from above, into their housing in the upper front side of the cocking slide bracket (711) and are held in place by the pin (723). Please note that, in case of a left-hand mounted cocking handle group [ 8 ] (also refer to § 12.2), the cocking slide bracket (711) is installed upside down so that the housing for the cocking slide plunger (721) and its spring (722) is at the lower side. When the cocking slide (712) is at its most forward position, the cocking slide plunger (721) engages the V-notch in the slide so that the slide, and therefore also the cocking handle (730), is held in place.

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MI.50 M2HB QCB machine gun

633 600 a

633 610

643 641 643

614

631

612 h b

a

660

639 632

668 666 667

b

V

642

II

VI

637 i

638

IV 634

d

III

c

23 x 635 614

614

g

h e

636

647 i

613

I 620

631 3100 (Fig. 2.c.1)

f

633 c

649 646 e

644

d

633 648

f

g

632

615

Fig. 2.j - Back plate group [ 9 ] Maintenance manual

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FN HERSTAL 2.2.

PARTS LISTS (continued)

2.2.9.

Back plate group [ 9 ]

MI.50 M2HB QCB machine gun

(a) List of parts (Fig. 2.j) CAT n° 600 610 612 613 614 615 620 631 632 633 634 635 636 637 638 639 641 642 643 644 646 647 648 649 660 666 667 668

Description

Qty per unit

Plate assembly, back, spade grip > Plate assembly, back > > Upper arm, handle > > Lower arm, handle > > Rivet, handle frame > Pin, locking > Sleeve, buffer tube assembly > Tube, handle grip, plate assembly back > Grip, handle, plastic > Screw, handle tube > Plate, buffer > Disk, buffer, fiber > Screw, adjusting, buffer disk > Plunger, adjusting screw > Spring, plunger, adjusting > Release, bolt latch > Trigger > Pin, trigger axis > Spring, compression, trigger > Lock, back plate latch > Spring, back plate latch lock > Pin, axis, lock, back plate > Latch, back plate > Spring, back plate latch > Safety assembly > > Slotted cheese head screw > > Hexagonal nut, style 1 > Hexagonal socket screw

1 1 1 (°) 1 (°) 4 (°) 1 1 2 2 4 1 23 1 1 1 1 1 2 2 1 1 1 1 1 1 1 1 2

(°) Although these components are available as spare parts, they are not discussed in the present maintenance manual : more information about their removal and/or replacement and the required tools is only available on special request.

(b) Description The back plate group [ 9 ] (catalog number (600)), mounted onto the rear part of the receiver (3100), is used to stop the bolt assembly (810) at the end of its rearward movement and to absorb its remaining recoil energy. In addition, the back plate group [ 9 ] has been provided with 2 handle grips and with the components allowing the operator to control the firing operation of the machine gun. Maintenance manual

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MI.50 M2HB QCB machine gun

633 600 a

633 610

643 641 643

614

631

612 h b

a

660

639 632

668 666 667

b

V

642

II

VI

637 i

638

IV 634

d

III

c

23 x 635 614

614

g

h e

636

647 i

613

I 620

631 3100 (Fig. 2.c.1)

f

633 c

649 646 e

644

d

633 648

f

g

632

615

Fig. 2.j - Back plate group [ 9 ] Maintenance manual

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MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.9.

Back plate group [ 9 ] (continued) (b) Description (continued) The back plate assembly (600) consists of the back plate subassembly (610) onto or into which the following assemblies and components have been installed : - The buffer tube sleeve (620) which is fitted, from the rear side, onto the buffer tube of the back plate subassembly (610) The buffer tube sleeve (620) is held into position on the buffer tube of the back plate subassembly (610) by the engagement of its stud (I) into the groove (II) in the buffer tube. The lock (III) of the buffer tube sleeve (620) can be used to lock the bolt latch release (639) at its lower position for automatic firing.

- The left and right handle grips (632) and their tubes (631) Each handle grip (632) is secured, together with its tube (631), between the corresponding extremities of the upper and lower handle arms (612) and (613) by means of 2 screws (633).

- The buffer plate (634) and the fiber buffer disks (635) provided inside the buffer tube of the back plate subassembly (610) These absorbing components are held in place by the buffer disks screw (636) used in combination with the plunger (637). The plunger (637) fits, together with its spring (638), into its housing (IV) in the buffer disks screw (636). The outer extremity of the plunger (637) engages one of the 2 grooves in the inner thread of the buffer tube of the back plate subassembly (610) in order to avoid that the buffer disks screw is loosened due to vibrations. The number of fiber buffer disks (635) (normally ‘23’) is determined so that the buffer disks screw (636) protrudes by 0 - 3.3 mm from the buffer tube of the back plate subassembly (610) when a torque of 40.7 ± 13.5 Nm is applied to it (also refer to § 9.9.2).

- The bolt latch release (639) and the trigger (641) which are secured by and can pivot around a pin (642) The bolt latch release (639) is located at the left side of the trigger (641) and both components are fitted together, from the rear side, into the upper opening (V) in the back plate subassembly (610). Both the bolt latch release (639) and the trigger (641) are held in position by a spring (643). The lower extremity of a spring (643) engages its housing in the bolt latch release (639) / the trigger (641) while the upper extremity of the spring engages the corresponding recess provided in the back plate subassembly (610). The front ends of both the bolt latch release (639) and the trigger (641) protrude from the front side of the back plate subassembly (610) (and therefore into the receiver (3100) when the back plate assembly (600) is installed onto the machine gun). The front end of the bolt latch release (639) is used to actuate the bolt latch (3838) (also refer to § 2.2.2.2). The front end of the trigger (641) is used to actuate the trigger bar (3846) (also refer to § 2.2.2.2).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

633 600 a

633 610

643 641 643

614

631

612 h b

a

660

639 632

668 666 667

b

V

642

II

VI

637 i

638

IV 634

d

III

c

23 x 635 614

614

g

h e

636

647 i

613

I 620

631 3100 (Fig. 2.c.1)

f

633 c

649 646 e

644

d

633 648

f

g

632

615

Fig. 2.j - Back plate group [ 9 ] Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

2.2.

PARTS LISTS (continued)

2.2.9.

Back plate group [ 9 ] (continued) (b) Description (continued) - The back plate latch (648) which is secured by and can pivot around a pin (642) The back plate latch (648), which is used to lock the back plate assembly (600) into position on the rear side of the receiver (3100), is held in position by its spring (649). The lower extremity of the back plate latch spring (649) engages its housing in the back plate latch (648) while the upper extremity of the spring engages the corresponding recess provided underneath the lower handle arm (613).

- The back plate latch lock (644) which is secured by and can pivot around the pin (647) which, on its turn, is secured by means of the locking pin (615) The back plate latch lock (644) (with its inner spring (646)) is used to lock the back plate latch (648) so that it becomes impossible to accidentally release the back plate assembly (600) by inadvertently moving the back plate latch.

- The safety assembly (660) which can be used to block the trigger (641) and which is fixed to the back plate subassembly (610) by means of the 2 screws (668) The trigger (641) is blocked when the safety catch (VI) is turned inwards so that the screw (666) is positioned under the trigger. When the screw (666) is installed correctly, it can be locked into position by using the hexagonal nut (667). When the safety catch (VI) is turned outwards, the trigger (641) is no longer blocked into position : a red warning dot will become visible.

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MI.50 M2HB QCB machine gun

THIS PAGE IS INTENTIONALLY BLANK

Maintenance manual

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MI.50 M2HB QCB machine gun

CHAPTER 3 : OPERATING PRINCIPLES 3.1.

EMPTY MACHINE GUN IN THE INITIAL CONDITION The initial condition of the machine gun is obtained after having carried out the unloading procedure (refer to § 6.4) and/or after having carried out the safety checks (refer to § 4.2). The functional parts of the machine gun are in the neutral position.

3.2.

LOADING AND COCKING THE MACHINE GUN Proceed as described in § 6.2. When the machine gun is cocked, the bolt (820) is at its front position and the sear (863) holds back the firing pin assembly (E2) at its cocked position.

3.3.

FIRING THE MACHINE GUN When firing the machine gun, the recoil force of the cartridge case causes the moving parts to be moved rearwards, compressing the driving spring assembly (870). In order to simplify the description of the several operations which take place simultaneously when firing the machine gun, the following operations will be described separately : • The operation of the moving parts (refer to § 3.3.1) : - Unlocking the bolt (820) at the beginning of the rearward movement of the moving parts - The operation of the accelerator (962) during the rearward movement of the moving parts - Buffering the rearward movement of the moving parts - The forward movement of the moving parts - Locking the bolt (820) at the end of the forward movement of the moving parts • The feeding operation (refer to § 3.3.2) : - Feeding the ammunition belt into the machine gun - Extraction of a cartridge from the ammunition belt and feeding the cartridge into the chamber - Extraction from the chamber and ejection of a cartridge case • The firing operation (refer to § 3.3.3) : - The cocking operation - The firing operation

Maintenance manual

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FN HERSTAL

MI.50 M2HB QCB machine gun

1

820

221

200

2

3816 110 110/1

3

230

912

900

820

Fig. 3.a - Unlocking the bolt (820) at the beginning of the rearward movement of the moving parts

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MI.50 M2HB QCB machine gun

3.3.

FIRING THE MACHINE GUN (continued)

3.3.1.

The operation of the moving parts The moving parts of the MI.50 M2HB QCB machine gun are the barrel extension group [ 3 ], the bolt group [ 5 ] and the buffer group [ 7 ].

(a) Unlocking the bolt (820) at the beginning of the rearward movement of the moving parts (Fig. 3.a) Just before the firing operation, the bolt (820) is locked to the barrel extension assembly (200) by means of the breech lock (221) (part ‘1’ of Fig. 3.a). The breech lock (221) is held upwards by means of the breech lock cam (3816) provided on the bottom of the receiver (3100).

At the instant of firing, the recoil force of the cartridge case causes the moving parts to be moved rearwards (part ‘1’ of Fig. 3.a). After the moving parts have moved approx. 20 mm rearwards, the breech lock pin (230), which holds the breech lock (221) in position in the barrel extension assembly (200), comes into contact with the inclined face of the front extremities of the breech lock depressors (912) of the buffer group (900) (part ‘2’ of Fig. 3.a). As a result, the breech lock pin (230), and therefore also the breech lock (221), will be pushed downwards resulting in the unlocking of the bolt (820). When the bolt (820) is unlocked, the assembly formed by the barrel (110) / (110/1) and the barrel extension assembly (200) is no longer linked to the bolt. This causes the bolt (820) to continue its rearward movement while the movement of the assembly formed by the barrel (110) / (110/1) and the barrel extension assembly (200) is absorbed and stopped by the buffer spring (963) (part of the buffer group (900)) (part ‘3’ of Fig. 3.a).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

110 110/1

820

962

b

950 200

A

A' > A

c

B B' >> B

c

Fig. 3.b - The operation of the accelerator (962) during the rearward movement of the moving parts

23 x 635

820

962

634

C1

930

G2

963

Fig. 3.c - Buffering the rearward movement of the moving parts Maintenance manual

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MI.50 M2HB QCB machine gun

3.3.

FIRING THE MACHINE GUN (continued)

3.3.1.

The operation of the moving parts (continued) (b) The operation of the accelerator (962) during the rearward movement of the moving parts (Fig. 3.b) During its rearward movement, the rear side of the barrel extension assembly (200) comes into contact with the front side of the accelerator (962) which is secured by and pivots on its pin (950). The contact with the rear side of the barrel extension assembly (200) causes the accelerator (962) to start rotating towards the rear side. During a part of the rearward movement of the moving parts, the nose of the accelerator (962) fits into the housing (b) in the bottom of the bolt (820) : the energy of the rotating accelerator will therefore be transferred to the bolt.

As long as the barrel extension assembly (200) continues moving rearwards, the contact point (c) between the rear side of the barrel extension assembly and the front side of the accelerator (962) moves downwards resulting in a faster and faster rearward movement of the nose of the accelerator. This causes the rearward movement of the bolt (820) to be accelerated until the accelerator (962) is turned so far that its nose is released from the housing (b) in the bottom of the bolt : the latter will then continue its faster rearward movement until the movement is absorbed and halted by the buffer plate (634) of the back plate assembly (600). After its nose has been released from the housing (b) in the bottom of the bolt (820), the accelerator (962) continues rotating until its claws lock the rear nose of the rear shank of the barrel extension body (C1) to the front nose of the buffer piston rod (930) causing the barrel extension assembly (200) to be locked to the buffer group (900) (also refer to Fig. 3.c).

(c) Buffering the rearward movement of the moving parts (Fig. 3.c) The rearward movement of the assembly formed by the barrel (110) / (110/1) and the barrel extension assembly (200) is absorbed and halted by the buffer piston assembly (G2), used in combination with the buffer spring (963). The rearward movement of the bolt (820) is absorbed and halted by the buffer plate (634), used in combination with the fiber buffer disks (635).

Maintenance manual

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MI.50 M2HB QCB machine gun

870

820

634 b

200

962

963

Fig. 3.d - The forward movement of the moving parts

221

820

a

3816

200

230

Fig. 3.e - Locking the bolt (820) at the end of the forward movement of the moving parts

Maintenance manual

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MI.50 M2HB QCB machine gun

3.3.

FIRING THE MACHINE GUN (continued)

3.3.1.

The operation of the moving parts (continued) (d) The forward movement of the moving parts (Fig. 3.d) The impact of the bolt (820) on the buffer plate (634) is partly buffered by the fiber buffer disks (635) while the remaining energy produced by the shock is returned to the bolt. This energy, combined with the energy of the compressed driving spring assembly (870), forces the bolt (820) to return forwards. During the forward movement of the bolt (820), the rear edge of the housing (b) in its bottom comes into contact with the nose of the accelerator (962) so that the latter is pushed back forwards and therefore unlocks the rear nose of the rear shank of the barrel extension body (C1) from the front nose of the buffer piston rod (930). Once the rear nose of the rear shank of the barrel extension body (C1) is unlocked from the front nose of the buffer piston rod (930), the assembly formed by the barrel (110) / (110/1) and the barrel extension assembly (200) is forced to return forwards by the compressed buffer spring (963). (e) Locking the bolt (820) at the end of the forward movement of the moving parts (Fig. 3.e) During the forward movement of the moving parts, the front bottom part of the breech lock (221) comes into contact with the inclined rear face of the protruding part (a) on top of the breech lock cam (3816). As a result, the breech lock (221) will be forced to engage the recess provided in the bottom of the bolt (820). When, approx. 15 mm before the end of the forward movement of the moving parts, the breech lock (221) is fully engaged in the recess in the bottom of the bolt (820), the latter is said to be ‘locked’ to the barrel extension assembly (200). When the moving parts reach their most forward position, the next cartridge can be fired.

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MI.50 M2HB QCB machine gun

471

a

810

D2 b 478

430

c 3600

During the rearward movement of the moving parts

D2 471 477

3828 3500

430

c

During the forward movement of the moving parts

Fig. 3.f - Feeding the ammunition belt into a left-hand fed machine gun Maintenance manual

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MI.50 M2HB QCB machine gun

3.3.

FIRING THE MACHINE GUN (continued)

3.3.2.

The feeding operation (a) Feeding the ammunition belt into the machine gun (Fig. 3.f) During the rearward movement of the moving parts and in case a cartridge is present at the ‘ammunition extraction’ position on the feed tray of the receiver (3100), this cartridge will be extracted from the ammunition belt as described in § 3.3.2 (b).

During the rearward movement of the moving parts, the rear end of the belt feed lever (471) moves in the groove (a) on top of the bolt assembly (810) : this causes the belt feed lever to pivot on its mounting pin (b) so that its front end moves towards the left side. As a result, the belt feed slide assembly (D2), which is actuated by the front end of the belt feed lever (471), is moved towards the left side so that the belt feed pawl (430) is forced to engage the next cartridge (c). The belt feed pawl (430) is first compressed, forced to pass over the next cartridge (c) and then engaged, by the force of the pawl spring (478), against the left side of the cartridge. During this operation, the ammunition belt is held back by the belt holding pawls assembly (3600). Please note that this operation corresponds to the standard case of a left-hand fed MI.50 M2HB QCB machine gun : if the gun is converted to right-hand feeding (also refer to § 12.1), the ‘rear right --> front left’ groove on top of the bolt assembly (810) will be used while, during the rearward movement of the moving parts, the front end of the belt feed lever (471) forces the belt feed slide assembly (D2) to move towards the right side.

During the forward movement of the moving parts, the front end of the belt feed lever (471) forces the belt feed slide assembly (D2) to move back towards the right (left-hand feed) / left (right-hand feed) side. As a result, the belt feed pawl (430) pushes the next cartridge (c), and therefore also the whole ammunition belt, laterally until the cartridge is correctly positioned at the ‘ammunition extraction’ position on the feed tray of the receiver (3100). For the standard case of a left-hand fed machine gun, this ‘ammunition extraction’ position is at the right side of the feed tray and obtained by full contact between the cartridge and both the front cartridge stop (3828) and the rear cartridge stop assembly (3500). If the gun is converted to right-hand feeding, the ‘ammunition extraction’ position is at the left side of the feed tray and obtained by full contact between the cartridge and the front cartridge stop (3828), the link stripper (3829) and the rear cartridge stop (3830). In order to obtain a correct positioning of the cartridge, the latter is held into contact with the feed tray itself by the belt feed pawl arm (477).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

1

MI.50 M2HB QCB machine gun

476

D1

840

820

2

3

D1

a

4

b 3836

d

5

820

c

842

e c

840 110 110/1

Fig. 3.g - Extraction of a cartridge from the ammunition belt and feeding the cartridge into the chamber

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MI.50 M2HB QCB machine gun

3.3.

FIRING THE MACHINE GUN (continued)

3.3.2.

The feeding operation (continued) (b) Extraction of a cartridge from the ammunition belt and feeding the cartridge into the chamber (Fig. 3.g) When the bolt (820) is at its most forward position, the extractor spring (476) forces the front end of the extractor/ejector assembly (840) to engage the rim of the cartridge presently positioned at the ‘ammunition extraction’ position on the feed tray of the receiver (3100) (part ‘1’ of Fig. 3.g). The extractor spring (476) is mounted inside the feed cover (D1) while the extractor/ejector assembly (840) has been provided on the left side of the bolt (820). For more information about the ‘ammunition extraction’ position on the feed tray of the receiver (3100), refer to § 3.3.2 (a).

At the beginning of the rearward movement of the moving parts, the extractor/ejector assembly (840) extracts the cartridge from the link (part ‘2’ of Fig. 3.g). During the rearward movement of the moving parts, the front end of the extractor/ejector assembly (840) is progressively forced down by the extractor guide cam (a) (part of the feed cover (D1)) so that the rim of the extracted cartridge is fitted into the T-slot (b) for the cartridges on the front face of the bolt (820) (part ‘3’ of Fig. 3.g). When the moving parts start their forward movement, the guide lug (c) on the left side of the front end of the extractor/ejector assembly (840) is in contact with the lower rear inclined face of the extractor switch (3836) : the front end of the extractor/ejector assembly is pushed fully downwards so that the cartridge is aligned with the axis of the barrel (110) / (110/1) and the cartridge case (d) of the previously fired cartridge is ejected (part ‘4’ of Fig. 3.g). During the forward movement of the moving parts, the cartridge is progressively inserted into the chamber (part ‘5’ of Fig. 3.g). When, during this forward movement of the moving parts, the guide lug (c) on the front end of the extractor/ejector assembly (840) comes into contact with the inclined face of the front extractor cam (e) provided inside the receiver (3100), the front end of the extractor/ejector assembly is forced to move back upwards (part ‘5’ of Fig. 3.g). (c) Extraction from the chamber and ejection of the cartridge case As it is fitted with its rim into the T-slot for the cartridges on the front face of the bolt (820), the cartridge case of the fired cartridge is extracted from the chamber during the rearward movement of the moving parts. During the forward movement of the moving parts, the cartridge case will then be pushed downwards along the T-slot and ejected when the next cartridge is aligned with the axis of the barrel (110) / (110/1) (also refer to part ‘4’ of Fig. 3.g). The last cartridge case (when there is no next cartridge in the T-slot) will be ejected by the ejector (842) of the extractor/ejector assembly (840) when the latter is pushed fully downwards by its contact with the lower rear inclined face of the extractor switch (3836). Maintenance manual

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MI.50 M2HB QCB machine gun

a

865

863

E2

Fig. 3.h - The cocking operation

3846 110 110/1

865

820

863

221

D2

3846

641

3700 863 E2

Fig. 3.i - Firing

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FN HERSTAL

MI.50 M2HB QCB machine gun

3.3.

FIRING THE MACHINE GUN (continued)

3.3.3.

The firing operation (a) The cocking operation (Fig. 3.h) During the rearward movement of the moving parts, the firing pin assembly (E2) is pushed, against the force of the firing pin spring (852), rearwards by the lower end of the cocking lever (865) until it is engaged by the sear (863). The position of the cocking lever (865) is determined by the engagement of its tip into the recess (a) provided in the mounting bracket which has been fixed to the inner side of the top plate of the receiver (3100).

(b) Firing (Fig. 3.i) When the moving parts are at their most forward position, the sear (863) comes into contact with the front end of the trigger bar (3846). When the trigger (641) is pushed down, its front end forces the rear end of the trigger bar (3846) to move upwards so that the front end of the trigger bar moves downwards and presses on the sear (863). The trigger bar (3846) pivots on its pin (3700). The upper limit position of the rear end of the trigger bar (3846) is determined by the position of the trigger bar stop knurled nut (3651) which is adjusted during the adjustment of the timing (also refer to § 10.5).

As a result, the sear (863) moves downwards, against the force of its spring (862), and releases the firing pin assembly (E2) which is propelled forwards by the force of the firing pin spring (852) : percussion takes place and the cartridge is fired. For more information about the 2 possible firing modes of the machine gun (single-shot and automatic), refer to § 6.3.

NOTE : The firing can only be initiated if the bolt (820) is positioned at its most forward position.

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MI.50 M2HB QCB machine gun

639

.

b

)

639 641

a

620

Fig. 4.a - Blocking the trigger (641) by means of the safety catch (a) (bolt latch release (639) unlocked and raised)

Fig. 4.b - Unlocking the bolt latch release (639) (if necessary)

D1

D1

c 3100

3100

440

Fig. 4.c - Checking if the feed tray (c) is empty

.

.

d

820

730 Fig. 4.d - Pulling the cocking handle (730) completely rearwards and then pushing it back forwards

Fig. 4.e - Checking if the chamber (d) and the front face of the bolt (820) are clear

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 4 : SAFETY INFORMATION 4.1.

WARNINGS AND CAUTIONS The following instructions should be read before loading and firing the weapon and before any intervention (disassembly, maintenance, ...) on it :

x The MI.50 M2HB QCB machine gun can cause injury or death up to 6800 metres. x Always handle the MI.50 M2HB QCB machine gun, like any other weapon, with extreme care and with the respect due to a loaded gun, even though you are certain the gun is unloaded. Never touch the trigger unless you are ready to fire. x Never modify parts of the gun. Repairs and disassembly exceeding the basic field stripping may only be carried out by qualified armourers or by FN HERSTAL. x If the weapon has been heavily oiled or greased for shipment or storage, clean it thoroughly and lightly lubricate the metal parts before firing. x The barrel should be perfectly dry before firing. x Never try to clear a barrel obstruction by firing.

4.2.

SAFETY CHECKS Carry out the following procedure in order to ensure that the MI.50 M2HB QCB machine gun can be manipulated, stored and/or transported without any risk : • Turn the safety catch (a) inwards under the trigger (641) so that the latter is blocked into position (Fig. 4.a). • Ensure that the bolt latch release (639) is unlocked and raised (Fig. 4.a). If the bolt latch release (639) is locked in its lower position by the lock (b) of the buffer tube sleeve (620), unlock it by turning the sleeve clockwise when viewed from the rear side (Fig. 4.b).

• Open the feed cover (D1) by turning its latch shaft (440) and then ensure that there is no ammunition on the feed tray (c) of the receiver (3100) (Fig. 4.c). Take into account that, after shooting , the barrel (110) / (110/1) can be very hot. If there is ammunition on the feed tray (c), unload the machine gun as described in § 6.4.

• Pull the cocking handle (730) completely rearwards and push it back forwards (Fig. 4.d). Please note that, after this operation, the bolt (820) is held back at its rear position.

• Ensure that the chamber (d) and the front face of the bolt (820) are free from ammunition (Fig. 4.e). If not, unload the machine gun as described in § 6.4.

• Pointing the gun in a safe direction, push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. Also unblock the trigger (641), push down on it to release the firing pin (861) and then block it again. Never close the feed cover (D1) with the bolt (820) held back at its rear position ! If, for any reason, the bolt (820) does not reach its most forward position and taking care not to trap the fingers, pull it forwards by inserting a screwdriver or a similar tool into its upper groove and using the upper plate of the receiver (3100) as a support.

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MI.50 M2HB QCB machine gun

820 YY-

ZZ

SY

YY

Y

YY

B1

Fig. 4.f - Checking if a correctly marked bolt (820) is used

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FN HERSTAL 4.2.

MI.50 M2HB QCB machine gun

SAFETY CHECKS (continued) • Ensure that the first four digits of the number combination marked on the upper front part of the bolt (820) correspond to the last four digits of the serial number of the machine gun (Fig. 4.f). The number combination marked on the upper front part of the bolt (820) is structured ‘ YYYY-ZZ’ where ‘YYYY’ represents the last four digits of the serial number of the machine gun and ‘ZZ’ represents the number of the presently used breech lock (221). The serial number of the machine gun has been marked in the front part of the upper rear plate of the receiver frame (B1) (‘SYYYY’ on F ig. 4.f). If the digits do not correspond, the machine gun should be restricted for further use and the following procedure should be carried out : - Remove the bolt assembly (810) and the barrel extension assembly (200) as described for ‘field stripping’ in § 7.1. - Reassemble the machine gun as described in § 7.2, especially taking into account the checks and the information given in the first step of the reassembling procedure.

• Close the feed cover (D1) and ensure that it locks correctly into position.

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MI.50 M2HB QCB machine gun

THIS PAGE IS INTENTIONALLY BLANK

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FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 5 : RECEPTION OF THE GUN Before any intervention on the MI.50 M2HB QCB machine gun, ensure to be familiar with the safety information given in chapter 4 of this maintenance manual.

• Take the packing case and inspect it for damage. If the packing case shows traces of deterioration, take note of them (detailed description or photo) and report it to FN Herstal.

• Open the packing case and check its contents according to the packing list. If there is a problem, report it to FN Herstal.

• Carry out the field stripping procedure (refer to chapter 7). If something seems abnormal, report it to FN Herstal.

• Clean the bore of the barrel (110) / (110/1) to remove the existing preservation lubricant. Remove the preservation lubricant from the bolt group [ 5 ]. For more detailed cleaning instructions, refer to chapter 8.

• Lubricate the bore of the barrel (110) / (110/1) and the bolt group [ 5 ] with a maintenance or functional lubricant. At this stage, the other parts of the MI.50 M2HB QCB machine gun do not require lubrication. For more detailed lubrication instructions, refer to chapter 8.

• Reassemble the machine gun.

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MI.50 M2HB QCB machine gun

523 a

541

522 520

Fig. 6.a - Rear sight leaf assembly (520) at its lowered position (*)

523 520

b

522 547

541

Fig. 6.b - Rear sight leaf assembly (520) at its raised position (*)

(*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, refer to § 13.1.4.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 6 : USING THE MACHINE GUN Before using the MI.50 M2HB QCB machine gun, ensure to be familiar with the safety information given in chapter 4 of this maintenance manual. Always ensure that the barrel group [ 1 ] has correctly been locked into position before shooting (for more information, refer to chapter 7).

6.1.

PREPARATORY OPERATIONS Mounting support Ensure that the MI.50 M2HB QCB machine gun has been correctly installed and, if necessary, locked onto its mounting support (tripod, weapon system, ...).

Barrel group [ 1 ] Ensure that the barrel group [ 1 ] has correctly been installed and locked into position. For more information about the correct installation of the barrel group [ 1 ], refer to its reinstallation described in chapter 7.

Rear sight assembly (500) (*) Set the rear sight assembly (500) for the correct shooting range taking into account the following points : • The rear sight leaf assembly (520) can be raised or lowered : - When the rear sight leaf assembly (520) is lowered, the peep-hole (a) of the rear sight slide (522) can be used as a fixed battlesight set for approx. 800 m (recommended for quick firing (combat situations, ...)) (Fig. 6.a). - When the rear sight leaf assembly (520) is raised, the peep-hole (b) of the rear sight slide (522) allows aiming the machine gun from 200 m to 1200 m in steps of 200 m and from 1200 m to 2500 m in steps of 100 m (Fig. 6.b). The rear sight slide (522) should be positioned according to the indications which can be found on the rear sight leaf (521).

• The rear sight slide (522) can be moved along the rear sight leaf (521) by turning the rear sight slide elevating knob (523). • If necessary, the rear sight windage knob (541) can be used to compensate the effects of sidewind on the trajectory of the bullet(s), especially in case of long-distance firing. In case of sidewind from the right/left side, the rear sight windage knob (541) should be turned clockwise/counterclockwise when viewed from the left side in order to move the rear sight leaf assembly (520) slightly towards the right/left side. If no sidewind correction is necessary, the mark on the rear sight leaf assembly (520) should be aligned with the ‘0’-line on the rear sight windage scale (547).

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FN HERSTAL

MI.50 M2HB QCB machine gun

b

a

Fig. 6.c - Ammunition belt

a

840

c 820

3100 3600 Fig. 6.d - Checking if the bolt (820) is at its front position

Fig. 6.e - Placing the ammunition belt onto the feed tray (c) of the receiver (3100) ((standard) left-hand feeding)

. .

. .

730

639

Fig. 6.f - Cocking the machine gun by using the cocking handle (730)

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FN HERSTAL 6.2.

MI.50 M2HB QCB machine gun

LOADING AND COCKING THE MACHINE GUN It is assumed that § 4.2. “Safety checks” has been carried out.

• Take an ammunition belt (Fig. 6.c). An ammunition belt has a double empty loop (a) at its right side and a single empty loop (b) at its left side. In case of a manually assembled ammunition belt, ensure that the rear ends of the cartridges of the belt are perfectly aligned with each other.

• Open the feed cover (D1) by turning its latch shaft (440) and then ensure that the bolt (820) is at its front position (Fig. 6.d). • Place the ammunition belt onto the feed tray (c) of the receiver (3100) so that the first cartridge is held by the belt holding pawls assembly (3600) (Fig. 6.e). For the (standard) left-hand fed MI.50 M2HB QCB machine gun, the ‘first cartridge’ is the cartridge with the double empty loop (a). For a right-hand fed machine gun, it is the cartridge with the single empty loop (b).

• Close the feed cover (D1) and ensure that it locks correctly into position. Never close the feed cover (D1) with the bolt (820) held back at its rear position !

NOTE : If necessary, it is also possible to load the ammunition belt without raising the feed cover (D1) : using both thumbs, and with the empty loop(s) first, push the first cartridge into the feed tray (c) and ensure that it is correctly engaged behind the spring-loaded belt holding pawls assembly (3600). • Cock the machine gun by proceeding as follows (Fig. 6.f) : - Pull the cocking handle (730) completely rearwards and push it back forwards. Please note that, after this operation, the bolt (820) is held back at its rear position.

- Push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. During this first back and forth movement of the bolt (820), the first cartridge will be moved sidewards on the feed tray (c) of the receiver (3100) until it is positioned at the correct position to be extracted from the ammunition belt.

- Pull the cocking handle (730) again completely rearwards and push it back forwards. During this second rearward movement of the bolt (820), the first cartridge will be extracted from the ammunition belt and will be fitted with its rim into the T-slot at the front side of the bolt. At the same time, the first link will be ejected from the machine gun. Ensure that the cocking handle (730) locks correctly into its front position and note that the bolt (820) is again held back at its rear position.

- Again push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. During this second forward movement of the bolt (820), the first cartridge will be pushed further downwards along the T-slot and then it will be pushed into the chamber of the barrel (110) / (110/1).

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MI.50 M2HB QCB machine gun

b 641

639

) a Fig. 6.g - Unblocking the trigger (641)

641

641

c

620

639 Fig. 6.h - Single-shot firing

639

Fig. 6.i - Automatic firing (bursts)

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FN HERSTAL 6.3.

MI.50 M2HB QCB machine gun

FIRING THE MACHINE GUN Ensure that § 8.2. “Cleaning and lubrication before firing” has been carried out.

• If not already done, load and cock the machine gun as described in § 6.2. • Turn the safety catch (a) outwards so that the trigger (641) is no longer blocked into position : a red warning dot (b) will become visible (Fig. 6.g).

Single-shot firing (Fig. 6.h) • Ensure that the bolt latch release (639) is unlocked and raised. This is the situation which is obtained after having carried out § 4.2. “Safety checks”.

• Aim the machine gun and then push down on the trigger (641) : the machine gun will fire a single shot. At the end of the firing cycle, the bolt latch (3838) will hold back the bolt (820) at its rear position so that the operation of the machine gun is stopped.

• For a next single shot, proceed as follows : - Push down on the bolt latch release (639) in order to raise the bolt latch (3838) and therefore release the bolt (820) so that the latter returns towards its front position. - Aim the machine gun and then push down on the trigger (641).

Automatic firing (bursts) (Fig. 6.i) • Push the bolt latch release (639) completely downwards and then turn the buffer tube sleeve (620) counterclockwise when viewed from the rear side until the lock (c) of the sleeve is positioned over the arm of the bolt latch release. • Release the bolt latch release (639) and ensure that it is held back (and therefore locked) in its lower position by the lock (c) of the buffer tube sleeve (620). • Aim the machine gun and then push down on the trigger (641) : the machine gun will start firing a burst. The lowered bolt latch release (639) keeps the bolt latch (3838) at the raised position so that the latch will not be able to hold back the bolt (820) at its rear position : the gun will continue firing until the trigger (641) is released or until all the ammunition has been used. Please note that, if the bolt latch release (639) is not locked in its lower position, bursts can also be fired by pushing down on both the bolt latch release (639) and the trigger (641).

NOTE : In case of intensive shooting, and in order to avoid excessive heating of the barrel (110) / (110/1), it is recommended to use more than one barrel group [ 1 ]. If the barrel (110) / (110/1) becomes overheated, there is also a risk of cook-off : unexpected firing of a round caused by the transmission of heat from the barrel towards the cartridge in the chamber. Optimal efficiency of the machine gun is obtained when firing short bursts. However, the MI.50 M2HB QCB machine gun can fire one 100-round single burst without any risk. For more information about the replacement of the barrel group [ 1 ], refer to chapter 7. If no spare barrel group [ 1 ] is used and after having used the whole ammunition belt, cooling down of the gun can be optimized by manually positioning the bolt (820) at its rear position (unlock the bolt latch release (639) and then pull the cocking handle (730) completely rearwards and push it back forwards). When using more than one barrel group [ 1 ], use them equally in order to avoid that one barrel group wears out more quickly than the other.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

639

.

b

)

639 641

a

620

Fig. 6.j - Blocking the trigger (641) by means of the safety catch (a) (bolt latch release (639) unlocked and raised)

D1

Fig. 6.k - Unlocking the bolt latch release (639) (if necessary)

840

.

.

c

3100

. 730

Fig. 6.l - Removing the ammunition belt from the feed tray (c)

Fig. 6.m - Pulling the cocking handle (730) completely rearwards and then pushing it back forwards

820

Fig. 6.n - Checking if the front face of the bolt (820) is clear Maintenance manual

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FN HERSTAL 6.4.

MI.50 M2HB QCB machine gun

UNLOADING THE MACHINE GUN • Turn the safety catch (a) inwards under the trigger (641) so that the latter is blocked into position (Fig. 6.j). • Ensure that the bolt latch release (639) is unlocked and raised (Fig. 6.j). If the bolt latch release (639) is locked in its lower position by the lock (b) of the buffer tube sleeve (620), unlock it by turning the sleeve clockwise when viewed from the rear side (Fig. 6.k).

NOTE : Take into account that, after shooting, the barrel (110) / (110/1) can be very hot. • Open the feed cover (D1) by turning its latch shaft (440) and then release and remove the ammunition belt (Fig. 6.l). To release the ammunition belt, it will be necessary to raise the extractor/ejector assembly (840) : do not forget to lower the assembly after having removed the ammunition belt. If present, remove any link from the feed tray (c) of the receiver (3100).

• Close the feed cover (D1) and ensure that it locks correctly into position. • Pull the cocking handle (730) completely rearwards and push it back forwards (Fig. 6.m). Please note that this will cause the extraction of any cartridge remaining in the chamber and that, after this operation, the bolt (820) is held back at its rear position.

• Push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. • Pull the cocking handle (730) again completely rearwards and push it back forwards. Please note that, after this operation, the bolt (820) is again held back at its rear position.

• Open the feed cover (D1) by turning its latch shaft (440). • Ensure that the front face of the bolt (820) is free from ammunition (Fig. 6.n). If there is a cartridge on the front face of the bolt (820), first try if it can be ejected by firing as described in § 6.3. For this try, take into account all the safety precautions and note that it is not necessary to load an ammunition belt. If the cartridge cannot be ejected by firing, and with the bolt (820) held back at its rear position, try to remove the cartridge by pushing downwards on the rim of its case with a tool such as a screwdriver or pliers. During this operation, NEVER touch the primer of the cartridge with the tool (in order to avoid any risk of explosion) and ensure that the barrel is ALWAYS pointing in a safe direction !

• Pointing the gun in a safe direction, push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. Also unblock the trigger (641), push down on it to release the firing pin (861) and then block it again. Never close the feed cover (D1) with the bolt (820) held back at its rear position ! If, for any reason, the bolt (820) does not reach its most forward position and taking care not to trap the fingers, pull it forwards by inserting a screwdriver or a similar tool into its upper groove and using the upper plate of the receiver (3100) as a support.

• Close the feed cover (D1) and ensure that it locks correctly into position. Maintenance manual

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MI.50 M2HB QCB machine gun

(

120

.

.

. 730

110 110/1 120

By using the cocking handle (730) and the carrying handle assembly (120)

By only using the carrying handle assembly (120)

Fig. 7.a - Unlocking the barrel (110) / (110/1)

120 [1]

. 3817

Fig. 7.b - Removal of the barrel group [ 1 ]

The texts and illustrations of this chapter apply to the (standard) left-hand fed MI.50 M2HB QCB machine gun. In case of a right-hand fed machine gun, the procedure is completely similar. Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 7 : FIELD STRIPPING Before any intervention on the MI.50 M2HB QCB machine gun, ensure to be familiar with the safety information given in chapter 4 of this maintenance manual.

7.1.

DISASSEMBLING THE MACHINE GUN It is very important to become familiar with the field stripping procedure of the machine gun as field stripping is required during the cleaning procedure which ensures reliable operation of the machine gun.

• If not already done, completely unload the machine gun (refer to § 6.4) and carry out the safety checks (refer to § 4.2). • While pushing the cocking handle (730) until it is positioned horizontally, unlock the barrel (110) / (110/1) by turning the carrying handle assembly (120) towards its vertical position (left part of Fig. 7.a). Using the carrying handle assembly (120) in its vertical position, take the barrel group [ 1 ] forwards out of the barrel support (3817) (Fig. 7.b) and then release the cocking handle (730). In fact, the barrel (110) / (110/1) is released from the front opening of the barrel extension body (C1) (also refer to § 2.2.3). If necessary, the barrel group [ 1 ] can also be removed by only using the carrying handle assembly (120) (in such a case, it is recommended to stand at the front side of the machine gun) : While firmly pushing the barrel group [ 1 ], by the carrying handle assembly (120), approx. 20 mm inwards, unlock the barrel (110) / (110/1) by turning the carrying handle assembly towards its vertical position (right part of Fig. 7.a). Using the carrying handle assembly (120) in its vertical position, take the barrel group [ 1 ] forwards out of the barrel support (3817) (Fig. 7.b). Finally, note that it is also possible to remove the barrel group [ 1 ] without using the carrying handle assembly (120) : just grip the barrel (110) / (110/1) firmly with both hands (in such a case, be extremely careful not to burn the hands if the machine gun has fired recently : if necessary, use anti-heat gloves !!).

• Open the feed cover (D1) by turning its latch shaft (440). • If, for any reason, the bolt (820) is held back at its rear position, proceed as follows to let it return towards its front position : - Pull the cocking handle (730) completely rearwards and hold it in that position. - Push down on the bolt latch release (639) in order to release the bolt (820) which will now be held back by the cocking handle (730). - Move the cocking handle (730) back forwards in order to guide the bolt (820) towards its front position. When the bolt (820) should be returned towards its front position with no barrel group [ 1 ] installed on the machine gun, always use this procedure with the cocking handle (730) to guide the bolt towards its front position ! It is absolutely necessary that the bolt (820) is at its front position in order to release the pressure on the driving spring assembly (870) so that the assembly can be removed (see further) without any risk.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

.

.

.

870

.

.

600

644 648

3100

3100

3838

Fig. 7.c - Unlocking and removing the back plate assembly (600)

Fig. 7.d - Unhooking and removing the driving spring assembly (870)

3100 a

.

b 725

961

3100 Fig. 7.e - Removal of the bolt stud (725)

Fig. 7.f - Unlocking and removing the moving parts

810

810

900

863

900

865

840

200 920

d

910

c C1

. 962

930

.

200

Fig. 7.g - Separating the moving parts Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 7.1.

MI.50 M2HB QCB machine gun

DISASSEMBLING THE MACHINE GUN (continued) • While pulling the back plate latch lock (644) rearwards and holding it in that position, raise the back plate latch (648) in order to unlock the back plate assembly (600) and then lift the assembly up and off the receiver (3100) (Fig. 7.c). • Ensure that the bolt (820) is at its front position (see before), release the rear end of the driving spring assembly (870) (push it first forwards and then slightly to the left) and then take the assembly out of the rear side of the bolt (820) and the receiver (3100) (Fig. 7.d). • Using the cocking handle (730), slowly move the bolt assembly (810) rearwards until the bolt stud (725) is aligned with the dismounting hole (a) in the slot in the side plate of the receiver (3100) (upper left part of Fig. 7.e). If, for any reason, the bolt (820) is moved too far rearwards and caught by the bolt latch (3838) (also refer to Fig. 7.d), push the rear end of the bolt latch upwards (some force may be required) to release the bolt and then push the latter back forwards.

• Through the dismounting hole (a), pull the bolt stud (725) out of the right side of the bolt (820) (upper left part of Fig. 7.e). In order not to lose the bolt stud (725), it is recommended to place it in the recess in the feed tray of the receiver (3100) (lower right part of Fig. 7.e).

• Using the stem of the driving spring assembly (870) or another similar pointed tool through the hole (b) in the right rear side of the receiver (3100), push the buffer body lock (961) inwards so that it no longer holds back the moving parts and simultaneously pull the moving parts out of the receiver (Fig. 7.f). When taking the moving parts out of the receiver (3100), take into account that they can fall apart.

• Slide the bolt assembly (810) rearwards off the barrel extension assembly (200) (Fig. 7.g). • If the firing pin (861) does not protrude from the front face of the bolt (820), use the tip of a screwdriver or a similar tool to push down on the sear (863) in order to release the firing pin. Before carrying out this operation and in order to avoid trapping the fingers by the rearward movement of the upper end of the cocking lever (865), first move the latter towards its rear position. After having removed the bolt assembly (810), place it on its right side in order to avoid that the extractor/ejector assembly (840) falls out.

• While turning the accelerator (962) completely forwards and slightly lowering the buffer group (900), release the buffer group from the barrel extension assembly (200) (Fig. 7.g). When turning the accelerator (962) completely forwards, its claws will release the rear shank (c) of the barrel extension body (C1). When, at the same time, the buffer group (900) is slightly lowered, the front nose (d) of the buffer piston rod (930) is released from the rear nose of the rear shank (c) of the barrel extension body (C1). During this step, hold the buffer body assembly (910) slightly inclined (front side downwards) so that the barrel buffer assembly (920) does not fall out of it.

• If not already done, slide the barrel buffer assembly (920) rearwards out of the buffer body assembly (910) (Fig. 7.g). This level of disassembly is sufficient to perform thorough cleaning : further disassembly should only be carried out by an authorized armourer or by FN HERSTAL. Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

YY

YY-

ZZ

820

SY YY Y

B1

ZZ

Upside down

221

YY

YY

C1

Fig. 7.h - Location of the serial number of the machine gun and the marks on the barrel extension body (C1), the breech lock (221) and the bolt (820)

863

810

865

840

900 920

b

912

910

c

200 C1

G1 a

930

962

.

.

810

940 900

200

Fig. 7.i - Reassembling the moving parts Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 7.2.

MI.50 M2HB QCB machine gun

REASSEMBLING THE MACHINE GUN • Ensure that the upper front part of the bolt (820) has been marked with the number combination ‘YYYY-ZZ’ where ‘YYYY’ represents the last four digits of the serial number of the machine gun and ‘ZZ’ represents the number of the breech lock (221) presently installed in the barrel extension body (C1) (Fig. 7.h). Ensure that the bottom of the barrel extension body (C1) has been marked with the last four digits of the serial number of the machine gun (‘YYYY’ on Fig. 7.h). The serial number of the machine gun has been marked in the front part of the upper rear plate of the receiver frame (B1) (‘SYYYY’ on Fig. 7.h). The number of the breech lock (221) has been marked in its cavity (‘ZZ’ on Fig. 7.h). If the bolt (820) has not been marked correctly, replace the bolt assembly (810) by an assembly with a correctly marked bolt. If the barrel extension body (C1) has not been marked correctly, replace the barrel extension assembly (200) by an assembly with a correctly marked barrel extension body. If there are no correctly marked parts available for the machine gun, it will be absolutely necessary to carry out the adjustment of the headspace described in § 10.4. During the adjustment procedure of the headspace, it will be asked to (change the) mark (of) the bolt (820) (as described in § 9.5.9) and/or the barrel extension body (C1) (as described in § 9.3.3).

• Ensure that all the components of the machine gun are perfectly clean. • From the rear side, insert the barrel buffer assembly (920) into the buffer body assembly (910) (Fig. 7.i). The guide lug (a) of the buffer spring guide (940) should be positioned at the right side so that it correctly engages the inside groove of the buffer body (G1). On the other hand, the front nose (b) of the buffer piston rod (930) should be facing upwards : if necessary, correctly orient the buffer piston rod by turning it manually.

• While holding the buffer group (900) inclined downwards at an angle of approx. 30° and while moving the accelerator (962) towards its horizontal position, reassemble the buffer group and the barrel extension assembly (200) by fitting the left and right breech lock depressors (912) of the buffer group into their housings in both sides of the barrel extension body (C1) (Fig. 7.i). Ensure that the narrower end of the rear shank (c) of the barrel extension body (C1) fits correctly between the 2 claws of the accelerator (962). Ensure that the front nose (b) of the buffer piston rod (930) engages correctly the rear nose of the rear shank (c) of the barrel extension body (C1).

• Push the buffer group (900) firmly onto the barrel extension assembly (200) until the accelerator (962) is rotated so that its 2 claws have locked themselves onto the rear shank (c) of the barrel extension body (C1). This causes the buffer group (900) to be locked to the barrel extension assembly (200).

• From the rear side, fit the bolt assembly (810) onto the barrel extension assembly (200) (Fig. 7.i). Ensure that the bolt assembly (810) fits correctly into the guides of the barrel extension body (C1) and push it forwards until the lowered extractor/ejector assembly (840) comes into contact with the front portion of the barrel extension body.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

810

MI.50 M2HB QCB machine gun

865

3838

.

.

961 Fig. 7.j - Pushing the cocking lever (865) completely forwards

Fig. 7.k - Reinserting the moving parts into the receiver (3100)

f

d

3100 e

725

820

725 Fig. 7.l - Reinstallation of the bolt stud (725)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 7.2.

MI.50 M2HB QCB machine gun

REASSEMBLING THE MACHINE GUN (continued) • Push the cocking lever (865) completely forwards (Fig. 7.j). NOTE : When reinstalling the moving parts into the receiver (3100), it is absolutely necessary that the cocking lever (865) is at its front position. If, by inadvertence, the weapon is reassembled with the cocking lever (865) at its rear position, the bolt assembly (810) will jam inside the receiver (3100) when the moving parts are completely reinserted into the machine gun ! In such a case, it will be necessary to carry out the ‘emergency’ procedure described further in this chapter (after the reinstallation of the bolt stud (725) and the complete reinsertion of the moving parts).

• While holding the moving parts slightly inclined (front side downwards) and while raising the bolt latch (3838) so that it does not hinder the insertion of the bolt assembly (810), reinsert the moving parts into the rear side of the receiver (3100) (Fig. 7.k). During this operation, the buffer body lock (961) will lock itself behind the rear end of the receiver (3100) holding back the moving parts inside the receiver.

• Fit the bolt stud (725), from the right side, into its hole (d) in the bolt (820) (left part of Fig. 7.l). • Using the bolt stud (725), move the bolt assembly (810) until the wider ring of the stud is aligned with the dismounting hole (e) in the slot in the side plate of the receiver (3100) (right part of Fig. 7.l). • Push the bolt stud (725) through the dismounting hole (e) as far as possible into its hole (d) in the bolt (820) (right part of Fig. 7.l). • While ensuring that the wider ring of the bolt stud (725) engages behind the slot in the side plate of the receiver (3100), use the bolt stud to push the bolt assembly (810) (and therefore also the moving parts) completely into the machine gun (right part of Fig. 7.l). If, by inadvertence and referring to the above note, the moving parts would have been reinserted with the cocking lever (865) at its rear position, the bolt assembly (810) has jammed inside the receiver (3100). In such a case, carry out the following ‘emergency’ procedure : - Remove the trigger bar (3846) as described in § 9.2.12. - Take the bolt handle (1075) and, at the right side of the machine gun, fit it onto the bolt stud (725). - Using the drift punch UT 2012 through the hole opposite to the hole (f) indicated in the right part of Fig. 7.l and looking, from the rear side, inside the receiver (3100), disengage the tip of the cocking lever (865) from the groove in the inner side of the upper rear plate of the receiver frame (B1) and hold it in that position. - Using the bolt handle (1075), pull the moving parts firmly rearwards in order to disengage them and then pull them out of the receiver (3100). - Reinstall the moving parts with a correctly positioned cocking lever (865) as described above.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

.

.

.

.

600

870

.

644 648

3100 Fig. 7.m - Reinstallation of the driving spring assembly (870)

3100

Fig. 7.n - Reinstallation of the back plate assembly (600)

)

120

.

. 730

110 110/1 120 Fig. 7.o - Reinstallation of the barrel group [ 1 ]

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 7.2.

MI.50 M2HB QCB machine gun

REASSEMBLING THE MACHINE GUN (continued) • From the rear side of the receiver (3100), and with its positioning pin pointing towards the right side, reinsert the driving spring assembly (870) into its housing in the right side of the bolt (820) (Fig. 7.m). • While compressing the driving spring assembly (870), secure it into position by engaging its positioning pin in the pin hole in the right inner side of the receiver (3100) (Fig. 7.m). • Reinstall the back plate assembly (600) by fitting it, from above, into its grooves at the rear side of the receiver (3100) (Fig. 7.n). Just before the back plate assembly (600) reaches its final lowered position, pull the back plate latch lock (644) rearwards and hold it in that position until the back plate assembly has correctly been locked into position by the back plate latch (648).

• Push the cocking handle (730) until it is positioned horizontally and hold it in that position (left part of Fig. 7.o). As a result, the moving parts are moved approx. 20 mm rearwards.

• Using the carrying handle assembly (120) at its vertical position, insert the barrel group [ 1 ] as far as possible into the front opening of the barrel support (3817) (left part of Fig. 7.o). • When the barrel group [ 1 ] is fully inserted, turn the carrying handle assembly (120) by 60° towards the left side (right part of Fig. 7.o). The barrel group [ 1 ] is fully inserted when the protruding extremity of the guide screw (3861) has reached the bent part of the slot in the barrel (110) / (110/1). The barrel group [ 1 ] is correctly locked into position when, inside the machine gun, the lug on the front end of the barrel locking spring blade (241) engages the corresponding notch in the rear end of the barrel (110) / (110/1). If the carrying handle assembly (120) is not turned towards the left side, the carrying handle (123) interferes with the line of sights of the machine gun indicating the shooter that the barrel group [ 1 ] has not been locked into position. Shooting with a not correctly locked barrel group [ 1 ] is very dangerous : it can cause the barrel group to jump out as well as injuries to the shooter and serious damage to the internal parts of the machine gun !

• Release the cocking handle (730). • Carry out § 4.2. “Safety checks”.

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

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Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

CHAPTER 8 : MAINTENANCE Before any intervention on the MI.50 M2HB QCB machine gun, ensure to be familiar with the safety information given in chapter 4 of this maintenance manual. The frequency at which the MI.50 M2HB QCB machine gun should be cleaned and lubricated depends on the ammunition used, the weather and shooting conditions and other external factors. When using normal ammunition under normal conditions, it is a good rule to clean and lubricate the machine gun after every use or, in case of intensive shooting, after each 1800 rounds : correct maintenance will enhance the longevity of the gun. Under normal conditions, it is recommended to lubricate all the friction surfaces. It is especially recommended to ensure that the inside of the feed cover (D1), the bolt assembly (810), the barrel extension assembly (200), the buffer group (900), the driving spring assembly (870), the extractor switch (3836), the breech lock cam (3816), the inner guides of the receiver (3100) and the back plate group [ 9 ] are correctly lubricated. NEVER use grease or oil on any part in contact with ammunition ! Under extreme climatic and combat conditions, it may be necessary to clean and lubricate more frequently.

Please note that, as long as it is applied to the correct surfaces or parts (not to the bore and the chamber of the barrel (110) / (110/1)), too much lubrication is never detrimental to the good operation of the machine gun. When it is not used, the machine gun should be stored in a clean and dry location. In such a case, and in order to ensure that the gun is always ready-to-use, it should be inspected, cleaned and lubricated regularly (interval depending on the storage conditions).

NOTE : When using blank ammunition, which results in a quicker soiling of a weapon, the cleaning frequency should be increased : the condition of the machine gun, and especially its lubrication, should be followed up all along the shooting sequence. Before cleaning the MI.50 M2HB QCB machine gun, ALWAYS ensure that it is unloaded (refer to § 6.4).

8.1.

LUBRICANT SPECIFICATIONS Lubrication

:

MIL-PRF-63460

(NATO S-758)

Preservation

:

MIL-PRF-63460

(NATO S-758)

Never use hydrocarbons, trichlorethylene nor ammonia : they could cause damage to the gun !

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun D1

a

450 c a NO LUBRICATION

475 e

840 d

474

b

865

e

b

f

842

i

200

E2

221

j

471

863

h j

b

g

d

i

b

h

b

820

962

n

l

n

p

k p

k

230 q

o

m

l

m

963

912

n q

950 870

900

q

w

w

u

639

641

NO LUBRICATION

r r t t

3836

u

[9] v

NO LUBRICATION

s

v

s

3816 s

3100

648

644

Fig. 8.a - Points to be lubricated before firing (if parts have been represented disassembled exceeding normal field stripping, this is only for reasons of clarity) Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 8.2.

MI.50 M2HB QCB machine gun

CLEANING AND LUBRICATION BEFORE FIRING The following procedure assumes that the MI.50 M2HB QCB machine gun has correctly been cleaned and lubricated the last time it has been used (also refer to § 8.3). If the MI.50 M2HB QCB machine gun is used for the first time upon purchase, it is assumed that the procedure described in chapter 5 has been carried out.

• Carry out the field stripping procedure as described in § 7.1. • Using the cleaning tools 1010 and clean rags (pieces of flannel), remove the maintenance lubricant from the bore and the chamber of the barrel (110) / (110/1) until the last rag is clean (also refer to § 8.3 (a)). • Dry the bore and the chamber of the barrel (110) / (110/1). • Remove the maintenance lubricant from the inside of the feed cover (D1), the bolt assembly (810), the barrel extension assembly (200), the buffer group (900), the driving spring assembly (870), the extractor switch (3836), the breech lock cam (3816), the inner guides of the receiver (3100) and the back plate group [ 9 ]. NOTE : When lubricating as explained below, NEVER apply lubricant to the front face of the bolt (820) and to the ammunition feeding and ejection section (‘NO LUBRICATION’ on Fig. 8.a). • Slightly lubricate by applying 1 or 2 drops of functional lubricant to (Fig. 8.a) : - the mechanism inside of the feed cover (D1) and especially the belt feed slide (450) (arrows ‘a’), the belt feed lever (471) (front and rear extremities and pivoting hole) and its pin (475) (arrows ‘b’) as well as the extractor guide cam (arrow ‘c’). - the pivoting point and the ejector (842) of the extractor/ejector assembly (840) (arrows ‘d’), the presently used free groove on top of the bolt (820) (arrows ‘e’), the cocking lever (865) and the upper end of the firing pin spring stop (868) (arrow ‘f’), the sear (863) (arrow ‘g’) and the firing pin assembly (E2) (reachable from underneath the bolt (arrows ‘h’)). - the sliding bottom surface of the bolt (820) (arrows ‘i’) and the corresponding sliding guides of the barrel extension assembly (200) (arrows ‘j’). - the sliding bottom surface of the barrel extension assembly (200) (arrows ‘k’). - the breech lock (221) and its pin (230) (located in the barrel extension assembly (200)) (arrows ‘l’) and the corresponding guides for the breech lock cam (3816) (arrows ‘m’). - the accelerator (962) and its pin (950) (arrows ‘n’), the buffer spring (963) (arrow ‘o’) and the breech lock depressors (912) (arrows ‘p’). - the driving spring assembly (870) (arrows ‘q’). - the extractor switch (3836) (arrows ‘r’), the breech lock cam (3816) (arrows ‘s’) as well as all the inner guides of the receiver (3100) (arrows ‘t’). - the sliding grooves of the back plate group [ 9 ] (arrows ‘u’). - the pivoting points of the back plate latch (648) and its lock (644) (arrows ‘v’). - the pivoting points of the bolt latch release (639) and the trigger (641) (arrows ‘w’). • Reassemble the machine gun as described in § 7.2. Before each shooting sequence, ALWAYS check the barrel (110) / (110/1) for obstructions and ensure that it is dry and clean. Maintenance manual

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FN HERSTAL

MI.50 M2HB QCB machine gun

1020 110 110/1

1050

1031 1040 Fig. 8.b - Using the cleaning tools 1020, 1031, 1040 and 1050 for a first cleaning of the barrel (110) / (110/1)

1020

110 110/1

1031 1010 1032

Fig. 8.c - Using the cleaning tools 1010 for the final cleaning of the barrel (110) / (110/1)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 8.3.

MI.50 M2HB QCB machine gun

CLEANING AND LUBRICATION AFTER FIRING • Carry out the field stripping procedure as described in § 7.1. (a) Barrel group [ 1 ] • Using the cleaning tools 1020, 1031, 1040 and 1050 (and a spray), apply solvent inside the bore and the chamber of the barrel (110) / (110/1) and let the product work a few minutes (Fig. 8.b). • Using the cleaning tools 1020, 1031, 1040 and 1050, remove as much as possible the solvent and the residues from the bore and the chamber of the barrel (110) / (110/1) (Fig. 8.b). • Using the cleaning tools 1010 and clean rags (pieces of flannel), clean the bore and the chamber of the barrel (110) / (110/1) until the last rag is clean (Fig. 8.c). • When the barrel (110) / (110/1) is clean, again use a piece of flannel, this time moistened with maintenance lubricant, to protect the bore and the chamber of the barrel until the next use. Please note that the bore and the chamber of the barrel (110) / (110/1) should be wiped dry before shooting (also refer to § 8.2).

• Clean the remaining part of the barrel group [ 1 ] with a soft, dry cloth. If necessary, use a soft solvent. In this case, ensure that the cleaned parts are perfectly dry before reassembling the machine gun.

• Protect the outside of the barrel group [ 1 ] by using a rag lightly moistened with maintenance lubricant. (b) Receiver group [ 2 ] • Clean with a soft, dry cloth. Pay special attention to the extractor switch (3836) (arrows ‘r’ on Fig. 8.a), the breech lock cam (3816) (arrows ‘s’) as well as all the inner guides of the receiver (3100) (arrows ‘t’). If necessary, use a soft solvent. In this case, ensure that the cleaned parts are perfectly dry before reassembling the machine gun.

NOTE : When lubricating as explained below, NEVER apply lubricant to the ammunition feeding and ejection section (‘NO LUBRICATION’ on Fig. 8.a). • Apply 1 or 2 drops of maintenance lubricant to the extractor switch (3836) (arrows ‘r’ on Fig. 8.a), the breech lock cam (3816) (arrows ‘s’) as well as all the inner guides of the receiver (3100) (arrows ‘t’).

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FN HERSTAL

MI.50 M2HB QCB machine gun

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Catalog n° 3660084070

FN HERSTAL 8.3.

MI.50 M2HB QCB machine gun

CLEANING AND LUBRICATION AFTER FIRING (continued) (c) Barrel extension group [ 3 ] • Clean with a soft, dry cloth. Pay special attention to the breech lock (221) and its pin (230) (arrows ‘l’ on Fig. 8.a), the corresponding guides for the breech lock cam (3816) (arrows ‘m’), the sliding bottom surface of the barrel extension assembly (200) (arrows ‘k’) and the sliding guides for the bolt (820) on the barrel extension assembly (arrows ‘j’).

• In case of important soiling of the barrel extension group [ 3 ], proceed as follows : - Remove the breech lock (221) as described in § 9.3.2. - Clean the barrel extension body (C1) as well as the disassembled components with a brush and/or a soft cloth. If necessary, use a soft solvent. In this case, ensure that the components are perfectly dry before reassembling them.

- Reinstall the breech lock (221) as described in § 9.3.2. • Apply 1 or 2 drops of maintenance lubricant to the breech lock (221) and its pin (230) (arrows ‘l’ on Fig. 8.a), the corresponding guides for the breech lock cam (3816) (arrows ‘m’), the sliding bottom surface of the barrel extension assembly (200) (arrows ‘k’) and the sliding guides for the bolt (820) on the barrel extension assembly (arrows ‘j’). (d) Feed cover group [ 4 ] • Clean with a soft, dry cloth. Pay special attention to the mechanism inside of the feed cover (D1) and especially the belt feed slide (450) (arrows ‘a’ on Fig. 8.a), the belt feed lever (471) (front and rear extremities and pivoting hole) and its pin (475) (arrows ‘b’) as well as the extractor guide cam (arrow ‘c’).

• In case of important soiling of the feed cover group [ 4 ], proceed as follows : - Disassemble the feed cover group [ 4 ] by carrying out the different removal and disassembly procedures given in § 9.4. Unless it is absolutely necessary, it is not recommended to remove the feed cover latch (479), the feed cover latch shaft (440) and their fixing components.

- Clean the feed cover body (410) as well as the disassembled components with a brush and/or a soft cloth. If necessary, use a soft solvent. In this case, ensure that the components are perfectly dry before reassembling them.

- Reassemble the feed cover group [ 4 ] by carrying out the different reinstallation and reassembly procedures given in § 9.4. • Apply 1 or 2 drops of maintenance lubricant to the mechanism inside of the feed cover (D1) and especially the belt feed slide (450) (arrows ‘a’ on Fig. 8.a), the belt feed lever (471) (front and rear extremities and pivoting hole) and its pin (475) (arrows ‘b’) as well as the extractor guide cam (arrow ‘c’). Maintenance manual

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FN HERSTAL

MI.50 M2HB QCB machine gun

820

1060

1071

1072

Fig. 8.d - Using the cleaning tools 1060 and 1071 to clean the hole for the firing pin (861) in the bolt (820)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 8.3.

MI.50 M2HB QCB machine gun

CLEANING AND LUBRICATION AFTER FIRING (continued) (e) Bolt group [ 5 ] • Clean with a soft, dry cloth. Pay special attention to the pivoting point and the ejector (842) of the extractor/ejector assembly (840) (arrows ‘d’ on Fig. 8.a), the presently used free groove on top of the bolt (820) (arrows ‘e’), the cocking lever (865) and the upper end of the firing pin spring stop (868) (arrow ‘f’), the sear (863) (arrow ‘g’), the firing pin assembly (E2) (reachable from underneath the bolt (arrows ‘h’)), the sliding bottom surface of the bolt (arrows ‘i’) and the driving spring assembly (870) (arrows ‘q’).

• If necessary, use a screwdriver to remove any carbon and other residues from the bolt assembly (810). • In case of important soiling of the bolt assembly (810), proceed as follows : - Completely disassemble the bolt assembly (810) by carrying out the different removal and disassembly procedures given in § 9.5. - Using the cleaning tools 1060 and 1071 from the rear side, clean the hole for the firing pin (861) in the bolt (820) (Fig. 8.d). - Clean the bolt (820) as well as the disassembled components with a brush and/or a soft cloth. If necessary, use a soft solvent. In this case, ensure that the components are perfectly dry before reassembling them.

- Reassemble the bolt assembly (810) by carrying out the different reinstallation and reassembly procedures given in § 9.5. NOTE : When lubricating as explained below, NEVER apply lubricant to the front face of the bolt (820) (‘NO LUBRICATION’ on Fig. 8.a). • Apply 1 or 2 drops of maintenance lubricant to the pivoting point and the ejector (842) of the extractor/ejector assembly (840) (arrows ‘d’ on Fig. 8.a), the presently used free groove on top of the bolt (820) (arrows ‘e’), the cocking lever (865) and the upper end of the firing pin spring stop (868) (arrow ‘f’), the sear (863) (arrow ‘g’), the firing pin assembly (E2) (reachable from underneath the bolt (arrows ‘h’)) and the sliding bottom surface of the bolt (arrows ‘i’). • Apply 1 or 2 drops of maintenance lubricant to the driving spring assembly (870) (arrows ‘q’).

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FN HERSTAL 8.3.

MI.50 M2HB QCB machine gun

CLEANING AND LUBRICATION AFTER FIRING (continued) (f) Rear sight group [ 6 ] (*) The following procedure should only be carried out in the very rare case of apparent soiling of the rear sight group [ 6 ]. Normally, a simple cleaning operation will be sufficient.

• Disassemble the rear sight group [ 6 ] by carrying out the different removal and disassembly procedures given in § 9.6. Unless it is absolutely necessary, it is not recommended to remove the rear sight windage scale (547).

• Clean the rear sight base (510) as well as the disassembled components with a brush and/or a soft cloth. If necessary, use a soft solvent. In this case, ensure that the components are perfectly dry before reassembling them.

• Reassemble the rear sight group [ 6 ] by carrying out the different reinstallation and reassembly procedures given in § 9.6. After any intervention on the rear sight group [ 6 ], the firing precision of the machine gun should be checked and, if necessary, adjusted as described in § 10.1 and § 10.2.

(*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, refer to § 13.1.5.

(g) Buffer group [ 7 ] Except the first and last steps, the following procedure should only be carried out in the very rare case of important soiling of the buffer group [ 7 ]. Normally, a simple cleaning and lubrication operation will be sufficient.

• Clean with a soft, dry cloth. Pay special attention to the accelerator (962) and its pin (950) (arrows ‘n’ on Fig. 8.a), the buffer spring (963) (arrow ‘o’) and the breech lock depressors (912) (arrows ‘p’).

• In case of exceptional soiling of the buffer group [ 7 ], proceed as follows : - Disassemble the buffer group [ 7 ] by carrying out the different removal and disassembly procedures given in § 9.7. Unless it is absolutely necessary, it is not recommended to remove the buffer body lock (961).

- Clean the buffer body (G1) as well as the disassembled components with a brush and/or a soft cloth. If necessary, use a soft solvent. In this case, ensure that the components are perfectly dry before reassembling them.

- Reassemble the buffer group [ 7 ] by carrying out the different reinstallation and reassembly procedures given in § 9.7. • Apply 1 or 2 drops of maintenance lubricant to the accelerator (962) and its pin (950) (arrows ‘n’ on Fig. 8.a), the buffer spring (963) (arrow ‘o’) and the breech lock depressors (912) (arrows ‘p’). Maintenance manual

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FN HERSTAL 8.3.

MI.50 M2HB QCB machine gun

CLEANING AND LUBRICATION AFTER FIRING (continued) (h) Cocking handle group [ 8 ] The following procedure should only be carried out in the very rare case of apparent soiling of the cocking handle group [ 8 ]. Normally, a simple cleaning operation will be sufficient.

• Disassemble the cocking handle group [ 8 ] by carrying out the different removal and disassembly procedures given in § 9.8. Unless it is absolutely necessary, it is not recommended to remove the cocking slide lever stud (714) and the cocking slide stop pin (724) and to separate the cocking slide lever (713) from the cocking handle (730).

• Clean the cocking slide bracket (711) as well as the disassembled components with a brush and/or a soft cloth. If necessary, use a soft solvent. In this case, ensure that the components are perfectly dry before reassembling them.

• Reassemble the cocking handle group [ 8 ] by carrying out the different reinstallation and reassembly procedures given in § 9.8. (i)

Back plate group [ 9 ] Except the first and last steps, the following procedure should only be carried out in the very rare case of important soiling of the back plate group [ 9 ]. Normally, a simple cleaning and lubrication operation will be sufficient. Please note that, as long as the inside parts of the back plate group [ 9 ] are not too soiled, outside soiling will not hinder its correct operation.

• Clean with a soft, dry cloth. Pay special attention to the sliding grooves of the back plate group [ 9 ] (arrows ‘u’ on Fig. 8.a), the pivoting points of the back plate latch (648) and its lock (644) (arrows ‘v’) and the pivoting points of the bolt latch release (639) and the trigger (641) (arrows ‘w’).

• In case of exceptional soiling of the back plate group [ 9 ], proceed as follows : - Completely disassemble the back plate group [ 9 ] by carrying out the different removal and disassembly procedures given in § 9.9. - Clean the back plate subassembly (610) as well as the disassembled components with a brush and/or a soft cloth. If necessary, use a soft solvent. In this case, ensure that the components are perfectly dry before reassembling them. Never use solvent on the fiber buffer disks (635) : just lightly lubricate them after cleaning.

- Reassemble the back plate group [ 9 ] by carrying out the different reinstallation and reassembly procedures given in § 9.9. • Apply 1 or 2 drops of maintenance lubricant to the sliding grooves of the back plate group [ 9 ] (arrows ‘u’ on Fig. 8.a), the pivoting points of the back plate latch (648) and its lock (644) (arrows ‘v’) and the pivoting points of the bolt latch release (639) and the trigger (641) (arrows ‘w’). • Reassemble the machine gun as described in § 7.2. Maintenance manual

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126

120

123 127

125

121

a

a

122

110 110/1

Fig. 9.1.a - Barrel group [ 1 ]

. .

125

110 110/1

120

Fig. 9.1.b - Removal of the carrying handle assembly (120)

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MI.50 M2HB QCB machine gun

CHAPTER 9 : DISASSEMBLY AND REASSEMBLY Before any intervention on the MI.50 M2HB QCB machine gun, ensure to be familiar with the safety information given in chapter 4 of this maintenance manual.

9.1.

BARREL GROUP [ 1 ] (Fig. 9.1.a)

9.1.1.

Removal and reinstallation of the carrying handle assembly (120) • Remove the barrel group [ 1 ] as described for ‘field stripping’ in § 7.1. • Unlock the carrying handle assembly (120) by raising the upper end of the carrying handle locking latch (125) and then slide the assembly forwards off the barrel (110) / (110/1) (Fig. 9.1.b). To reassemble, follow the above steps in reverse order, taking into account the following points (Fig. 9.1.c) : - When fitting the carrying handle assembly (120) back into position, ensure that its rear lug (a) correctly engages the notch (b) provided in the barrel (110) / (110/1). - The carrying handle assembly (120) is only correctly locked into position when the wider part of the carrying handle locking latch (125) correctly engages the groove (c) provided in the barrel (110) / (110/1).

125 a

110 110/1

120

.

b

c

Fig. 9.1.c - Reinstallation of the carrying handle assembly (120)

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122

.

125

UT 2008 121 Fig. 9.1.d - Removal of the carrying handle locking latch (125)

127

123

126

. 127

121

Fig. 9.1.f - Removal of the carrying handle (123) from the stem of the carrying handle body (121)

120

Fig. 9.1.e - Unscrewing the nut (127)

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9.1.

BARREL GROUP [ 1 ] (continued)

9.1.2.

Removal and reinstallation of the carrying handle locking latch (125) Requirements : • UT 2008 (Drift punch, dia. 1.9 mm, lg 25 mm) • UT 2111 (Hammer 250 g) • Remove the barrel group [ 1 ] as described for ‘field stripping’ in § 7.1. • Remove the carrying handle assembly (120) as described in § 9.1.1. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the carrying handle assembly (120) can be fixed into a vice. When fixing the carrying handle assembly (120) into a vice, use special clamps or a rag to avoid scratches.

• Using the drift punch UT 2008 and the hammer UT 2111, drive out the spring pin (122) (Fig. 9.1.d). NOTE : Once it has been removed, the spring pin (122) must always be replaced by a new one ! • When withdrawing the drift punch UT 2008, the carrying handle locking latch (125) will be released from the carrying handle body (121) (Fig. 9.1.d). To reassemble, follow the above steps in reverse order.

9.1.3.

Removal and reinstallation of the carrying handle (123) Requirements : • UT 1304 (Straight box wrench 12 x 13 mm) • UT 1425 (Bar, dia. 6 mm) • Remove the barrel group [ 1 ] as described for ‘field stripping’ in § 7.1. • Remove the carrying handle assembly (120) as described in § 9.1.1. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the carrying handle assembly (120) can be fixed into a vice. When fixing the carrying handle assembly (120) into a vice, use special clamps or a rag to avoid scratches.

• Using the wrench UT 1304 together with the bar UT 1425, unscrew the nut (127) (Fig. 9.1.e). • Taking care not to lose the washer (126), pull the carrying handle (123) off the stem of the carrying handle body (121). To reassemble, follow the above steps in reverse order.

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3500

3505

b

B2 c

3834

3828

a

3504

b

B1

d c

3503

d

3502 a

3835

Fig. 9.2.a - Rear cartridge stop assembly (3500) and front cartridge stop (3828)

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9.2.

RECEIVER GROUP [ 2 ]

9.2.1.

Removal and reinstallation of the rear cartridge stop assembly (3500) and the front cartridge stop (3828) This procedure applies to the (standard) left-hand fed MI.50 M2HB QCB machine gun. In case of a right-hand fed machine gun, refer to § 12.1.

Requirements : • UT 1803 (Half-round nose pliers) • Open the feed cover (D1) by turning its latch shaft (440). • At the right side of the ammunition feeding and ejection section of the receiver frame (B1) and using the pliers UT 1803, pull the locking pin (3834) out of the front end of the right mounting pin (3835) (left part of Fig. 9.2.b). • Taking into account that the front cartridge stop (3828) and then the rear cartridge stop assembly (3500) will be released, withdraw the right mounting pin (3835) by pulling it rearwards (Fig. 9.2.b). • Remove the rear cartridge stop assembly (3500) and the front cartridge stop (3828). To reassemble, follow the above steps in reverse order, taking into account the following points : - Ensure that the rear cartridge stop assembly (3500) and the front cartridge stop (3828) are oriented correctly and that they are installed into the correct mounting slots. - Ensure that the locking pin (3834) fits correctly into position.

UT 1803

. B1

3500 3834 3835

3835

3828 3834

Fig. 9.2.b - Removal of the rear cartridge stop assembly (3500) and the front cartridge stop (3828)

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UT 2010

B2

3505

. 3502 3502

3505

3504 3503

Fig. 9.2.c - Disassembling the rear cartridge stop assembly (3500)

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9.2.

RECEIVER GROUP [ 2 ] (continued)

9.2.2.

Disassembling and reassembling the rear cartridge stop assembly (3500) Requirements : • • • •

OREA 722 (Center punch, round-end) UT 1803 (Half-round nose pliers) UT 2010 (Drift punch, dia. 2.9 mm, lg 40 mm) UT 2111 (Hammer 250 g)

• Remove the rear cartridge stop assembly (3500) as described in § 9.2.1. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the rear cartridge stop assembly (3500) can be fixed into a vice. When fixing the rear cartridge stop assembly (3500) into a vice, use special clamps or a rag to avoid scratches.

• Using the drift punch UT 2010 and the hammer UT 2111, drive out the pin (3505) (left part of Fig. 9.2.c). Take into account that the extremities of the pin (3505) have been staked.

NOTE : Once it has been removed, the pin (3505) must always be replaced by a new one ! • While holding the cartridge aligning pawl (3502) in position with a finger, withdraw the drift punch UT 2010. • Gently release and then remove the cartridge aligning pawl (3502), its plunger (3503) and its spring (3504) from the rear cartridge stop (B2) (right part of Fig. 9.2.c). To reassemble, follow the above steps in reverse order, taking into account the following points : - The cartridge aligning pawl spring (3504) should fit into the plunger (3503) which, on its turn, should fit into the corresponding housing in the cartridge aligning pawl (3502). - After its reinstallation, secure the pin (3505) by staking its extremities by using the center punch OREA 722 and the hammer UT 2111.

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MI.50 M2HB QCB machine gun

3834 c b

B1

d

b

3603

a

3601

3602

c

a

3835

3600 3827

d

Fig. 9.2.d - Belt holding pawls assembly (3600)

UT 1803 a

.

3834

B1

3835 3834

3600

3835

3601

3602 3827

3603

3827

Fig. 9.2.e - Removal of the left and right belt holding pawls (3601) and (3602)

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9.2.

RECEIVER GROUP [ 2 ] (continued)

9.2.3.

Removal and reinstallation of the left and right belt holding pawls (3601) and (3602) This procedure applies to the (standard) left-hand fed MI.50 M2HB QCB machine gun. In case of a right-hand fed machine gun, refer to § 12.1.

Requirements : • UT 1803 (Half-round nose pliers) • Open the feed cover (D1) by turning its latch shaft (440). • At the left side of the ammunition feeding and ejection section of the receiver frame (B1) and using the pliers UT 1803, pull the locking pin (3834) out of the front end of the left mounting pin (3835) (left part of Fig. 9.2.e). • While holding the belt holding pawls assembly (3600) in position with a finger, withdraw the left mounting pin (3835) by pulling it rearwards (Fig. 9.2.e). Take into account that the belt holding pawls assembly (3600) is subjected to the force of the pawl springs (3827).

• Remove the belt holding pawls assembly (3600) together with the 2 pawl springs (3827). • Separate the belt holding pawls assembly (3600) into the left belt holding pawl (3601), the right belt holding pawl (3602) and the belt holding pawls sleeve (3603) (right part of Fig. 9.2.e). To reassemble, follow the above steps in reverse order, taking into account the following points : - Slightly lubricate the 2 pawl springs (3827) before reinstalling them into their holes (a) (right part of Fig. 9.2.e). - Ensure that the locking pin (3834) fits correctly into position.

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MI.50 M2HB QCB machine gun

UT 2301

UT 2322 UT 2301

UT 2322

3861

OREA 235

OREA 235 b

3861

3863 3817

a 3863

Fig. 9.2.f - Removal of the guide screw (3861) and the safety washer (3863)

a

Fig. 9.2.g - Reinstallation of the guide screw (3861) and the safety washer (3863)

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MI.50 M2HB QCB machine gun

9.2.

RECEIVER GROUP [ 2 ] (continued)

9.2.4.

Removal and reinstallation of the guide screw (3861) and the safety washer (3863) Requirements : • • • • • • •

OREA 235 (Screwdriver 13x3.8 (hexagonal tip) modified) OREA 721 (Center punch, flat-end) OREA 722 (Center punch, round-end) UT 2111 (Hammer 250 g) UT 2301 (Torque wrench) UT 2322 (Screwdriver socket, torque wrench, 1/2”) Screwdriver or similar tool

• Remove the barrel group [ 1 ] as described for ‘field stripping’ in § 7.1. • Using a screwdriver or a similar tool, release the 2 tabs (a) of the safety washer (3863) from the groove of the guide screw (3861) (Fig. 9.2.f). • Using the torque wrench UT 2301 (with socket UT 2322 and tip OREA 235), unscrew and remove the guide screw (3861) together with the safety washer (3863) from the barrel support (3817) (Fig. 9.2.f). NOTE : Once it has been removed, the safety washer (3863) must always be replaced by a new one ! To reassemble, follow the above steps in reverse order, taking into account the following points (Fig. 9.2.g) : - When reinstalling a new safety washer (3863), its tabs (a) should be pointing upwards. - When tightening the guide screw (3861), first apply a torque of 20 Nm by using the torque wrench UT 2301 (with socket UT 2322 and tip OREA 235) and then push the 2 tabs (a) of the safety washer (3863) into the groove of the guide screw by using the center punch OREA 721 and the hammer UT 2111. After that, determine which recess (b) in the barrel support body is most distant from the groove of the guide screw (3861) and then secure the safety washer (3863) by staking its edge into that recess by using the center punch OREA 722 and the hammer UT 2111.

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MI.50 M2HB QCB machine gun

UT 1803 B1

3823

3821 3821

3823

B1

3817 Fig. 9.2.h - Unlocking the barrel support (3817) by disengaging the locking pin (3821)

c

b b a

3100

a c

OREA 742

.

d

3817 .

f

g

e i h

Fig. 9.2.i - Loosening the barrel support (3817) Maintenance manual

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MI.50 M2HB QCB machine gun

9.2.

RECEIVER GROUP [ 2 ] (continued)

9.2.5.

Removal of the barrel support (3817) and the shim (3818) Requirements : • • • •

OREA 742 (Tooling for sleeve support, barrel) UT 1803 (Half-round nose pliers) In case of ‘anti-aircraft sights’-kit, requirements of § 13.1.6 (a) If necessary, requirements of § 9.2.4

• Remove the barrel group [ 1 ], the back plate assembly (600), the driving spring assembly (870) and the moving parts as described for ‘field stripping’ in § 7.1. • In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, remove the ring sight assembly (1400) as described in § 13.1.6 (a). Please note that the illustrations of § 9.2.5 to § 9.2.8 show the receiver (3100) with the (standard) front sight (3824).

• If necessary, remove the guide screw (3861) and the safety washer (3863) as described in § 9.2.4. • Turn the machine gun upside down. • Underneath the machine gun, and in order to unlock the barrel support (3817), disengage the locking pin (3821) by proceeding as follows : - Using the pliers UT 1803, unbend the extremities of the split pin (3823) and straighten them (left part of Fig. 9.2.h). - Pull the locking pin (3821) rearwards and then turn it so that it is held back at its rear position by the contact between the straightened extremities of the split pin (3823) and the receiver frame (B1) (right part of Fig. 9.2.h). If the locking pin (3821) is blocked and cannot be pulled rearwards, push it rearwards by using a pointed tool such as a drift punch through the lower hole in the flange of the barrel support (3817).

• Loosen the barrel support (3817) by proceeding as follows : - Fix the supporting part of the tool OREA 742 into a vice or on a tripod, unscrew the nut (a) and then, without removing the bush (b), remove the screw (c) of the tool. After that, pull the rod (d) out of the right side of the tool (upper left part of Fig. 9.2.i). - Fit the machine gun with the front part of its receiver (3100) into the fork of the tool OREA 742, align the front mounting hole in the receiver with the holes in the tool and then secure by using the screw (c) (inserted from the right side) and the nut (a) (upper right part of Fig. 9.2.i). - Fit the ring of the tool OREA 742 onto the barrel support (3817) as shown in the middle part of Fig. 9.2.i, fit the fork-headed screw (e) between the 2 flanges of the ring and then insert the pin (f) into the closest hole (g) of the ring (lower left part of Fig. 9.2.i). - Turning the crank (h) of the tool, fit the fork-headed screw (e) onto the pin (f) (lower left part of Fig. 9.2.i). - Continue turning the crank (h) in order to loosen the barrel support (3817) by approx. 45° in the counterclockwise direction when viewed from the front side (lower right part of Fig. 9.2.i). - Turn the crank (h) back by a few turns in order to release the fork-headed screw (e) from the pin (f), move the pin towards the next hole (i) and then repeat the 2 previous steps in order to loosen the barrel support (3817) by another 1/8 turn. - Repeat this operation until the barrel support (3817) can be unscrewed manually or by using a rod inserted into its holes. Maintenance manual

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.

3817

3100 3818 Fig. 9.2.j - Removal of the barrel support (3817) and the shim (3818)

3818

o

3100

OREA 742 Fig. 9.2.k - Reinstallation of the shim (3818)

3817 3818

◊

3100 3817

OREA 742 Fig. 9.2.l - Reinstalling the barrel support (3817) and manually tightening it Maintenance manual

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9.2.

RECEIVER GROUP [ 2 ] (continued)

9.2.5.

Removal of the barrel support (3817) and the shim (3818) (continued) • Using the ring of the tool OREA 742 or a rod inserted into its holes, completely unscrew the barrel support (3817) from the threaded cylindrical mounting support at the front side of the receiver (3100) (Fig. 9.2.j). • Remove the shim (3818) from the receiver (3100) (Fig. 9.2.j).

9.2.6.

Reinstallation of the barrel support (3817) and the shim (3818) Requirements : • • • •

OREA 742 (Tooling for sleeve support, barrel) UT 1803 (Half-round nose pliers) In case of ‘anti-aircraft sights’-kit, requirements of § 13.1.6 (a) If necessary, requirements of § 9.2.4

Before reinstalling the barrel support (3817), ensure that it is perfectly clean : pay special attention to its inner rear thread as well as to its contact surface with the shim (3818). Also ensure that the outer thread of the cylindrical mounting support at the front side of the receiver (3100) is perfectly clean. It is assumed that the receiver (3100) is still secured into the fork of the supporting part of the tool OREA 742 (also refer to § 9.2.5).

• Fit the shim (3818) onto the threaded cylindrical mounting support at the front side of the receiver (3100) (Fig. 9.2.k). Ensure that the shim (3818) is oriented correctly : the chamfered side of its large opening should be facing towards the receiver (3100) while the small hole (o) for the locking pin (3821) should be at the lower side. Also ensure that the shim (3818) fits correctly into the fork of the tool OREA 742 and that its small hole (o) is correctly aligned with the hole with the locking pin (3821) in the front side of the receiver (3100).

• Lightly lubricate the outer thread of the cylindrical mounting support at the front side of the receiver (3100). • Screw the barrel support (3817) onto the cylindrical mounting support at the front side of the receiver (3100) and then, by using the ring of the tool OREA 742, tighten it manually against the shim (3818) (left part of Fig. 9.2.l). • Looking from the front side, check if the barrel support (3817) is oriented as shown in the right part of Fig. 9.2.l. The corner (◊) of the barrel support (3817) should be located at 4 to 5 mm from the imaginary vertical central line of the machine gun.

If so, directly proceed to the following step. If not, the presently installed shim (3818) should be replaced by another one by proceeding as follows : - Completely unscrew the barrel support (3817). - Replace the presently installed shim (3818) by another one. Twelve different shims (3818/1 to 1318/12 (recognizable by an engraved number)) are available and, in increasing numerical order, the thickness of each shim increases by 0.06 - 0.07 mm. This corresponds to a modification of the angular position of the tightened barrel support (3817) by 15° - 17°.

- Screw the barrel support (3817) back into position and check its orientation as described above. Maintenance manual

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c

MI.50 M2HB QCB machine gun

OREA 742 d

.

.

3817

j

OREA 742

f

f

e h Fig. 9.2.m - Final tightening and correct positioning of the barrel support (3817)

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MI.50 M2HB QCB machine gun

9.2.

RECEIVER GROUP [ 2 ] (continued)

9.2.6.

Reinstallation of the barrel support (3817) and the shim (3818) (continued) • From the right side, insert the rod (d) completely into its hole just underneath the screw (c) of the tool OREA 742 (upper left part of Fig. 9.2.m). The rod (d) will actuate the head of the split pin (3823) so that the split pin is turned. As a result, the straightened extremities of the split pin will lose contact with the receiver frame (B1) so that they no longer hold back the locking pin (3821) at its rear position : the locking pin will therefore be pushed forwards by the force of the locking spring (3822) and held back by the body of the barrel support (3817) itself as the corresponding groove in the support is not aligned with the locking pin yet.

• With the ring of the tool OREA 742 fitted onto the barrel support (3817), fit the forkheaded screw (e) between the 2 flanges of the ring and then insert the pin (f) into the closest hole (j) of the ring as shown in the middle and right parts of Fig. 9.2.m. • Turning the crank (h) of the tool, fit the fork-headed screw (e) onto the pin (f) (right part of Fig. 9.2.m). • Continue turning the crank (h) in order to tighten the barrel support (3817) in the clockwise direction when viewed from the front side until the barrel support is positioned correctly (Fig. 9.2.m). When the barrel support (3817) reaches its correct position, the locking pin (3821) will engage, by the force of the locking spring (3822), into one of the 2 grooves at the rear side of the barrel support body so that the barrel support is locked into position.

• Turn the crank (h) back by a few turns in order to release the fork-headed screw (e) from the pin (f), remove the pin and then slide the ring of the tool OREA 742 off the barrel support (3817). • Unscrew the nut (a) and then, without removing the bush (b), remove the screw (c) of the tool in order to release the machine gun from the tool. • Take the machine gun out of the supporting part of the tool OREA 742 and then reinstall the screw (c) (inserted from the right side) and the nut (a). • Underneath the machine gun, ensure that the locking pin (3821) has correctly engaged one of the 2 grooves at the rear side of the barrel support body and then, using the pliers UT 1803, lock the split pin (3823) by bending its 2 extremities. • If they have been removed, reinstall the (new) safety washer (3863) and the guide screw (3861) as described in § 9.2.4. • In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, reinstall the ring sight assembly (1400) as described in § 13.1.6 (a). • Reassemble the machine gun as described for ‘field stripping’ in § 7.2.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

UT 1913 OREA 228 3820

B1

3819

OREA 742

Fig. 9.2.n - Removal of the breech bearing (3819)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.2.

RECEIVER GROUP [ 2 ] (continued)

9.2.7.

Removal of the breech bearing (3819) Requirements : • • • • • •

OREA 228 (Wrench for ring guide, barrel MI.50) OREA 742 (Tooling for sleeve support, barrel) UT 1803 (Half-round nose pliers) UT 1913 (Screwdriver 5.5 x 150 mm) In case of ‘anti-aircraft sights’-kit, requirements of § 13.1.6 (a) If necessary, requirements of § 9.2.4

• Remove the barrel support (3817) as described in § 9.2.5. It is assumed that the receiver (3100) is still secured into the fork of the supporting part of the tool OREA 742 (also refer to § 9.2.5).

• Using the screwdriver UT 1913, take out the breech bearing locking screw (3820) (left part of Fig. 9.2.n). • Using the wrench OREA 228, screw the breech bearing (3819) out of the threaded cylindrical mounting support at the front side of the receiver frame (B1) (right part of Fig. 9.2.n).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

UT 2442

OREA 742

3819

OREA 228

UT 1913 3820

B1

OREA 742

3819

Fig. 9.2.o - Reinstallation of the breech bearing (3819) and, if it is replaced by a new one, also drilling it

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.2.

RECEIVER GROUP [ 2 ] (continued)

9.2.8.

Reinstallation of the breech bearing (3819) Requirements : • • • • • • •

OREA 228 (Wrench for ring guide, barrel) OREA 742 (Tooling for sleeve support, barrel) UT 1803 (Half-round nose pliers) UT 1913 (Screwdriver 5.5 x 150 mm) If necessary, UT 2442 (Twist drill, dia. 5.1 mm) In case of ‘anti-aircraft sights’-kit, requirements of § 13.1.6 (a) If necessary, requirements of § 9.2.4

Before reinstalling the breech bearing (3819), ensure that it is perfectly clean : pay special attention to its outer rear thread. Also ensure that the inner thread of the cylindrical mounting support at the front side of the receiver frame (B1) is perfectly clean. It is assumed that the receiver frame (B1) is still secured into the fork of the supporting part of the tool OREA 742 (also refer to § 9.2.5).

• Lightly lubricate the inner thread of the cylindrical mounting support at the front side of the receiver frame (B1). • Screw the breech bearing (3819) into the threaded cylindrical mounting support at the front side of the receiver frame (B1) and then, by using the wrench OREA 228, tighten it against the receiver (upper left part of Fig. 9.2.o). • If the breech bearing (3819) is not replaced by a new one, ensure that its hole for its locking screw (3820) is perfectly aligned with the corresponding hole in the receiver frame (B1). If necessary, loosen the breech bearing (3819) in order to obtain a perfect alignment of the holes.

If the breech bearing (3819) is replaced by a new one, and using the drill UT 2442 through the corresponding hole in the receiver frame (B1), drill into the bearing in order to create a hole for the breech bearing locking screw (3820) (upper right part of Fig. 9.2.o). After having drilled, remove any drilling residues.

• Using the screwdriver UT 1913, screw the breech bearing locking screw (3820) fully home (lower part of Fig. 9.2.o). Ensure that the breech bearing locking screw (3820) does not protrude inside the mounting support of the receiver frame (B1). If the screw protrudes (especially when it has been replaced by a new one), it should be filed until it has a length of 5.45 ± 0.25 mm.

• Reinstall the barrel support (3817) as described in § 9.2.6. • Reassemble the machine gun as described for ‘field stripping’ in § 7.2.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

UT 1803 3822 3821

3823

. Fig. 9.2.p - Removal of the locking pin (3821)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.2.

RECEIVER GROUP [ 2 ] (continued)

9.2.9.

Removal and reinstallation of the locking pin (3821) Requirements : • • • •

OREA 742 (Tooling for sleeve support, barrel) UT 1803 (Half-round nose pliers) In case of ‘anti-aircraft sights’-kit, requirements of § 13.1.6 (a) If necessary, requirements of § 9.2.4

• Remove the barrel support (3817) as described in § 9.2.5. • Take the machine gun out of the supporting part of the tool OREA 742. • Turn the machine gun upside down. Please note that, in order to unlock the barrel support (3817), the locking pin (3821) has been pulled back at its rear position and held there by means of the split pin (3823) (also refer to § 9.2.5).

• Release the locking pin (3821) by turning it. The straightened extremities of the split pin (3823) will lose contact with the receiver frame (B1) so that the locking pin (3821) will be pushed forwards by the force of the locking spring (3822).

• Push the locking pin (3821) rearwards so that the locking spring (3822) is compressed and, as a result, the pressure on the split pin (3823) is released. • Using the pliers UT 1803, pull the split pin (3823) out of the rear end of the locking pin (3821) (Fig. 9.2.p). • Gently release the pressure on the locking pin (3821) and then take it, together with the locking spring (3822) out of the front side of the receiver frame (B1) (Fig. 9.2.p). To reassemble, follow the above steps in reverse order, taking into account the following points : - Lightly lubricate the locking pin (3821) and the locking spring (3822) before reinstalling them. - After its reinstallation, and in order to allow the reinstallation of the barrel support (3817), the locking pin (3821) should be pushed and held back at its rear position. Therefore, do not bend the extremities of the split pin (3823) yet : the split pin with straight extremities will be used to hold back the locking pin (also refer to § 9.2.5 and § 9.2.6).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

.

UT 1803

MI.50 M2HB QCB machine gun

3813

3814

3816

3812 3813 3816 B1

3815

3813

3812 3814

Fig. 9.2.q - Removal of the breech lock cam (3816) and the locking spring (3812)

3812

3813

3816 b B1 a

3814

3814 UT 2203 B1

3815

3816 3813

Fig. 9.2.r - Reinstallation of the breech lock cam (3816) and the locking spring (3812) Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 9.2.

MI.50 M2HB QCB machine gun

RECEIVER GROUP [ 2 ] (continued)

9.2.10. Removal of the breech lock cam (3816) and the locking spring (3812) Requirements : • UT 1039 (Combination wrench 1 1/8”) • UT 1803 (Half-round nose pliers) • UT 1910 (Screwdriver 10 x 200 mm) • Open the feed cover (D1) by turning its latch shaft (440). • Remove the barrel group [ 1 ], the back plate assembly (600), the driving spring assembly (870) and the moving parts as described for ‘field stripping’ in § 7.1. • Underneath the receiver frame (B1) and using the pliers UT 1803, unbend the split pin (3815) and then pull the pin out of the nut (3814) and the lower end of the screw (3813) (left part of Fig. 9.2.q). • Using the wrench UT 1039 and the screwdriver UT 1910 and taking into account that the locking spring (3812) will be released, unscrew the nut (3814) from the screw (3813) (Fig. 9.2.q). • Take the screw (3813) and the breech lock cam (3816) out of the inside of the receiver frame (B1) (Fig. 9.2.q).

9.2.11. Reinstallation of the breech lock cam (3816) and the locking spring (3812) Requirements : • • • •

UT 1039 (Combination wrench 1 1/8”) UT 1803 (Half-round nose pliers) UT 1910 (Screwdriver 10 x 200 mm) UT 2203 (Feeler gauge)

• Fit the protruding bottom part (a) of the breech lock cam (3816) into the elongated transversal hole in the bottom plate of the receiver frame (B1) and then, from the inside, insert the screw (3813) into the hole (b) of the breech lock cam (upper parts of Fig. 9.2.r). • From underneath, fit the locking spring (3812), with the screw hole at the front side and its folded ends facing outwards, onto the screw (3813) and then screw the nut (3814), with its grooves facing inwards, onto the screw (Fig. 9.2.r). • Using the wrench UT 1039 and the screwdriver UT 1910, tighten the nut (3814) onto the screw (3813). Ensure that, at the end of this operation, one of the grooves of the nut (3814) is perfectly aligned with the hole in the screw (3813).

• Using the feeler gauge UT 2203 in the middle of the notch in the bottom plate of the receiver frame (B1), check if the clearance between the breech lock cam (3816) and the bottom plate lays between 0.05 and 0.20 mm (lower left part of Fig. 9.2.r). If the 0.05 mm thickness does not pass, unscrew the nut (3814) by 1/6 of a turn and then check again. If the 0.20 mm thickness passes, tighten the nut (3814) by 1/6 of a turn and then check again. If it is impossible to obtain a correct clearance, replace the screw (3813).

• Insert the split pin (3815) into the aligned groove of the nut (3814) and hole of the screw (3813) and then, using the pliers UT 1803, lock it by bending its 2 extremities (lower right part of Fig. 9.2.r). • Reinstall the barrel group [ 1 ], the back plate assembly (600), the driving spring assembly (870) and the moving parts as described for ‘field stripping’ in § 7.2. • Close the feed cover (D1) and ensure that it locks correctly into position. Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

3700

. a

b

3846

B1

Fig. 9.2.s - Removal of the trigger bar (3846)

3653

UT 1910 3654

500

B1

B5

3651

Fig. 9.2.t - Removal of the trigger bar stop knurled nut (3651) and the trigger bar stop bracket (3653)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 9.2.

MI.50 M2HB QCB machine gun

RECEIVER GROUP [ 2 ] (continued)

9.2.12. Removal and reinstallation of the trigger bar (3846) • Remove the barrel group [ 1 ], the back plate assembly (600), the driving spring assembly (870) and the moving parts as described for ‘field stripping’ in § 7.1. Although, for reasons of clarity, Fig. 9.2.s shows the receiver (3100) without trigger bar stop assembly (B5), it is not necessary to remove this assembly.

• At the left side of the receiver frame (B1), turn the trigger bar pin (3700) in order to align its little protruding part (a) with the notch (b) of its mounting hole in the receiver (Fig. 9.2.s). • While holding the trigger bar (3846) in position with a finger, withdraw the trigger bar pin (3700) (Fig. 9.2.s). • Take the trigger bar (3846) out of the rear side of the receiver frame (B1) (Fig. 9.2.s). To reassemble, follow the above steps in reverse order, taking into account the following points : - When reinstalling the trigger bar (3846), ensure that it fits correctly into the inner groove at the upper rear side of the receiver frame (B1). - After it has been inserted fully into position, secure the trigger bar pin (3700) by turning it.

9.2.13. Removal and reinstallation of the trigger bar stop knurled nut (3651) and the trigger bar stop bracket (3653) Requirements : • • • •

UT 1910 (Screwdriver 10 x 200 mm) UT 2030 (Center punch, dia. 6 mm) UT 2111 (Hammer 250 g) Requirements of § 10.5

• Remove the trigger bar (3846) as described in § 9.2.12. • Using the screwdriver UT 1910 and taking into account that it also secures the rear end of the rear sight assembly (500) (or (1500/1) if the machine gun is equipped with the ‘antiaircraft sights’-kit), take out the screw (3654) in order to remove the trigger bar stop assembly (B5) from the inner upper rear part of the receiver frame (B1) (left part of Fig. 9.2.t). Take into account that the head of the screw (3654) has been staked.

• Unscrew the trigger bar stop knurled nut (3651) from the threaded pin of the trigger bar stop bracket (3653) (right part of Fig. 9.2.t). To reassemble, follow the above steps in reverse order, taking into account the following points : - After having reassembled the trigger bar stop assembly (B5), reinstall it by proceeding as described in § 10.5. ‘Timing adjustment’. - After its reinstallation, secure the screw (3654) by staking its head by using the center punch UT 2030 and the hammer UT 2111. After any intervention on the trigger bar stop knurled nut (3651), the timing of the machine gun should be checked and, if necessary, adjusted as described in § 10.5.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

.

3826 OREA 255

3854

. UT 2012 a B1

3825 b

3824

3854

3824 3826

3854

3825

Fig. 9.2.u - Removal of the front sight (3824), the front sight cover (3826) and the front sight base (3854) (*)

(*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, refer to § 13.1.6.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 9.2.

MI.50 M2HB QCB machine gun

RECEIVER GROUP [ 2 ] (continued)

9.2.14. Removal and reinstallation of the front sight (3824), the front sight cover (3826) and the front sight base (3854) (*) Requirements : • OREA 255 (Wrench, front sight) • UT 2012 (Drift punch, dia. 3.5 mm, lg 27 mm) • UT 2111 (Hammer 250 g) NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the machine gun can be fixed into a vice. When fixing the machine gun into a vice, use special clamps or a rag to avoid scratches.

• If necessary, and using the OREA 255 through the upper hole in the front sight cover (3826), screw the front sight (3824) out of the front sight base (3854) (upper left part of Fig. 9.2.u). Please note that, as long as the front sight (3824) has not been screwed, the removal and reinstallation of the assembly formed by the front sight base (3854) and the front sight will not affect the firing precision : the present step can therefore be skipped in order to avoid the necessity of checking and, if necessary, adjusting the firing precision of the machine gun. Also note that, when the front sight base (3854) has been removed from the receiver frame (B1), it is also possible to turn the front sight (3824) by using a screwdriver from underneath.

• Using the drift punch UT 2012 and the hammer UT 2111, drive out the 2 spring pins (3825) (upper right part of Fig. 9.2.u). NOTE : Once they have been removed, the spring pins (3825) must always be replaced by new ones ! • After the second withdrawal of the drift punch UT 2012, the front sight cover (3826) and then the front sight base (3854) can be lifted up and off the receiver frame (B1) (Fig. 9.2.u). To reassemble, follow the above steps in reverse order, taking into account the following points : - If the front sight (3824) has been separated from the front sight base (3854), it can only be reinstalled by screwing it from underneath into the front sight base. - The front sight base (3854) should fit into the central groove (a) at the upper front side of the receiver frame (B1) while the front sight cover (3826) should fit into the 2 outer grooves (b) (Fig. 9.2.u). If the front sight (3824) has been screwed, the firing precision of the machine gun should be checked and, if necessary, adjusted as described in § 10.1 and § 10.2.

9.2.15. Removal and reinstallation of the cover pawl (3831) and its spring (3832) The cover pawl (3831) and its spring (3832) can be removed after having removed the feed cover (D1) (also refer to § 9.4.1). If they have been removed, the cover pawl (3831) and its spring (3832) should be reinstalled into their housing in the upper front side of the receiver frame (B1) before reinstalling the feed cover (D1). When reinstalling the cover pawl (3831), its notch should be facing outwards.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

3845

3841

3843 a

a

3842

3844 3839

b

B4

b

3840 3838

Fig. 9.2.v - Bolt latch assembly (B4)

3844

3845

. 3838

3839

UT 1803 3844

3839

. B1 3841 OREA 558

3843 3842

3839 3838

3840

3844 3845

Fig. 9.2.w - Removal and disassembly of the bolt latch assembly (B4) Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 9.2.

MI.50 M2HB QCB machine gun

RECEIVER GROUP [ 2 ] (continued)

9.2.16. Removal/disassembly and reassembly/reinstallation of the bolt latch assembly (B4) Requirements : • • • • • • •

OREA 270 (Wrench, nut, bolt latch rod) OREA 558 (Tool, assembling, bolt latch, .50 machine gun) UT 1803 (Half-round nose pliers) UT 1910 (Screwdriver 10 x 200 mm) UT 2030 (Center punch, dia. 6 mm) UT 2111 (Hammer 250 g) Requirements of § 10.5

• Open the feed cover (D1) by turning its latch shaft (440). • Remove the barrel group [ 1 ], the back plate assembly (600), the driving spring assembly (870) and the moving parts as described for ‘field stripping’ in § 7.1. Please note that it is now possible to simply remove the bolt latch (3838) (together with its plunger (3841) and the corresponding spring (3842)) by first removing the trigger bar (3846) (refer to § 9.2.12) and then pushing out the pin (3840) by using a pointed tool such as a drift punch through the corresponding hole provided in the side plate of the receiver frame (B1).

• Remove the trigger bar stop knurled nut (3651) as described in § 9.2.13. • At the rear side of the receiver frame (B1), fit the OREA 558 into the grooves for the back plate assembly (600) (upper left part of Fig. 9.2.w). If necessary, turn the handle of the OREA 558 in order to unscrew its threaded rod so that it does not come into contact with the receiver frame (B1) when installing the tool.

• Using its handle, screw the threaded rod of the OREA 558 inwards until it comes into contact with the bolt latch (3838) (upper left part of Fig. 9.2.w). • Continue screwing the handle of the OREA 558 in order to push the bolt latch rod (3839), against the force of its spring (3843), forwards until the bolt latch rod nut (3844) comes out of the front side of the bolt latch mounting bracket and becomes easily accessible through the feed cover opening (upper right parts of Fig. 9.2.w). • Using the pliers UT 1803, unbend the split pin (3845) and then pull the pin out of the front end of the bolt latch rod (3839) and its nut (3844) (upper right parts of Fig. 9.2.w). • Using the wrench OREA 270 through the feed cover opening, loosen and then remove the bolt latch rod nut (3844). • Using its handle, unscrew the threaded rod of the OREA 558 (the pressure on the bolt latch rod spring (3843) will be released) until the tool can be removed and then lift the tool up and off the rear side of the receiver frame (B1). • Taking care not to lose the bolt latch plunger (3841) and its spring (3842), take the remaining parts of the bolt latch assembly (B4) out of the rear side of the bolt latch mounting bracket (lower part of Fig. 9.2.w). • Disassemble the bolt latch assembly (B4) as shown in the lower part of Fig. 9.2.w. In order to separate the bolt latch rod (3839) from the bolt latch (3838), push out the pin (3840) by using a pointed tool such as a drift punch.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

3836 3833

B1

3849

UT 1803

b a B1

3833 UT 1175

3837

3836

Fig. 9.2.x - Removal of the extractor switch (3836) and its spring (3837)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 9.2.

MI.50 M2HB QCB machine gun

RECEIVER GROUP [ 2 ] (continued)

9.2.16. Removal/disassembly and reassembly/reinstallation of the bolt latch assembly (B4) (continued) To reassemble, follow the above steps in reverse order, taking into account the following points : - When fitting the bolt latch assembly (B4) back into the rear side of the bolt latch mounting bracket, the bolt latch (3838) will hang down : it should be raised manually in order to be correctly engaged by the threaded rod of the OREA 558 when the tool is used to push the bolt latch rod (3839) forwards, against the force of its spring (3843). - When reinstalling the bolt latch rod nut (3844), first fully tighten it and then, if necessary, loosen it slightly in order to obtain a perfect alignment of its front groove with the hole in the front end of the bolt latch rod (3839).

9.2.17. Removal of the extractor switch (3836) and its spring (3837) Requirements : • UT 1175 (Open-end wrench 1/2 x 9/16”) • UT 1803 (Half-round nose pliers) • Open the feed cover (D1) by turning its latch shaft (440). • Remove the barrel group [ 1 ], the back plate assembly (600), the driving spring assembly (870) and the moving parts as described for ‘field stripping’ in § 7.1. • At the left side of the receiver frame (B1) and using the pliers UT 1803, remove the safety spring (3849) from the nut (3833) (upper left part of Fig. 9.2.x). • Using the wrench UT 1175, unscrew the nut (3833) from the extractor switch (3836) (lower left part of Fig. 9.2.x). • Through the feed cover opening, take the extractor switch (3836) and its spring (3837) out of the inner left side of the receiver frame (B1) (right part of Fig. 9.2.x).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

e

c

3836

MI.50 M2HB QCB machine gun

3836 d

f

3837

B1

UT 1803

3849

3833 e

UT 1175

Fig. 9.2.y - Reinstallation of the extractor switch (3836) and its spring (3837)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL 9.2.

MI.50 M2HB QCB machine gun

RECEIVER GROUP [ 2 ] (continued)

9.2.18. Reinstallation of the extractor switch (3836) and its spring (3837) Requirements : • UT 1175 (Open-end wrench 1/2 x 9/16”) • UT 1803 (Half-round nose pliers) • Screwdriver or similar tool • Fit the extractor switch spring (3837) into position in the groove in the inner side of the left side plate of the receiver frame (B1) (upper left part of Fig. 9.2.y). Ensure that the little curved extremity (a) of the extractor switch spring (3837) fits correctly into its hole (b) provided in the groove (also refer to the right part of Fig. 9.2.x).

• From the inside of the receiver frame (B1), fit the extractor switch (3836) back into position (upper parts of Fig. 9.2.y). While pushing down the free extremity (d) of the extractor switch spring (3837) by using a tool such as a screwdriver, locate the shoulder (c) of the extractor switch (3836) onto the extremity (d) and then fit the pin (e) of the extractor switch into its hole (f) in the receiver frame (B1). At the same time, fit the shoulder (c) of the extractor switch (3836) into position in the groove.

• At the left outer side of the receiver frame (B1), screw the nut (3833), with its grooves facing outwards, onto the pin (e) of the extractor switch (3836) (lower left part of Fig. 9.2.y). • Using the wrench UT 1175, fully tighten the nut (3833) onto the pin (e) of the extractor switch (3836) and then loosen it by 60° (lower left part of Fig. 9.2.y). Ensure that, at the end of this operation, one of the grooves of the nut (3833) is perfectly aligned with the hole in the pin (e) of the extractor switch (3836). Do not tighten too much : ensure that the extractor switch (3836) can operate freely.

• Fit the safety spring (3849) into the aligned groove of the nut (3833) and hole in the pin (e) of the extractor switch (3836) and then, using the pliers UT 1803, install the safety spring correctly onto the nut (lower right part of Fig. 9.2.y). • Reinstall the barrel group [ 1 ], the back plate assembly (600), the driving spring assembly (870) and the moving parts as described for ‘field stripping’ in § 7.2. • Close the feed cover (D1) and ensure that it locks correctly into position.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

241 C1

a

221/13 221/14 221/15 221/16 221/17 221/18

201 a

221/19 221/20 221/21 221/22 221/23

221/24 221/25 221/26 221/27 221/28

b

230 200

b

233

Fig. 9.3.a - Barrel extension group [ 3 ]

C1

UT 2008

. 241

Fig. 9.3.b - Removal of the barrel locking spring blade (241)

The barrel extension assembly (200) may never be interchanged between different machine guns : it must always be used with the same gun (and especially with the same bolt assembly (810)) ! For more information about the marks used to ensure this requirement, refer to § 7.2 and to § 9.3.3.

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FN HERSTAL

MI.50 M2HB QCB machine gun

9.3.

BARREL EXTENSION GROUP [ 3 ] (Fig. 9.3.a)

9.3.1.

Removal and reinstallation of the barrel locking spring blade (241) As the barrel locking spring blade (241) is held into position by staking, only remove it when it is absolutely necessary !

Requirements : • • • •

OREA 722 (Center punch, round-end) UT 2008 (Drift punch, dia. 1.9 mm, lg 25 mm) UT 2111 (Hammer 250 g) Screwdriver or similar tool

• Remove the barrel extension assembly (200) as described for ‘field stripping’ in § 7.1. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the barrel extension assembly (200) can be fixed into a vice. When fixing the barrel extension assembly (200) into a vice, use special clamps or a rag to avoid scratches.

• Using a tool such as a screwdriver at the right side of the barrel extension assembly (200), unbend the staking which holds the barrel locking spring blade (241) into position. • Using the drift punch UT 2008 and the hammer UT 2111, drive the barrel locking spring blade (241) forwards out of its housing in the right side of the barrel extension body (C1) (Fig. 9.3.b). To reassemble, follow the above steps in reverse order, taking into account the following points (Fig. 9.3.c) : - The barrel locking spring blade (241) should be oriented so that its lug (a) is facing inwards. - After having inserted the barrel locking spring blade (241) completely into its housing (b) in the right side of the barrel extension body (C1), secure it into position by staking. Using the center punch OREA 722 and the hammer UT 2111, stake material from the edge of the housing (b) into the not yet used notch (c) of the barrel locking spring blade (241). The same notch (c) should never be used twice.

c

b

UT 2008

C1

a 241 241 Fig. 9.3.c - Reinstallation of the barrel locking spring blade (241) Maintenance manual

- 155 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

UT 2006

UT 2004

221

. 221 C1

. 230

C1

221

233

230 Fig. 9.3.d - Removal of the breech lock (221)

OREA 870

.

221

233 Fig. 9.3.e - Installing a new spring pin (233) by using the drift pin OREA 870 Maintenance manual

- 156 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.3.

BARREL EXTENSION GROUP [ 3 ] (continued)

9.3.2.

Removal and reinstallation of the breech lock (221) NOTE : Take into account that, if the breech lock (221) will be replaced by a new one, the adjustment of the headspace should be carried out : the presently installed breech lock will not necessarily be replaced by an identical one. Requirements : • • • • •

OREA 870 (Drift-pin, placement pin, breech lock pin) UT 2004 (Drift punch, dia. 5 mm, lg 40 mm) UT 2006 (Drift punch, dia. 2.4 mm, lg 21 mm) UT 2111 (Hammer 250 g) If necessary, requirements of § 10.4

• Remove the barrel extension assembly (200) as described for ‘field stripping’ in § 7.1. • Using the drift punch UT 2006 and the hammer UT 2111 from underneath, drive the spring pin (233) out of the breech lock pin (230) and into the body of the breech lock (221) (upper left part of Fig. 9.3.d). NOTE : Once it has been removed, the spring pin (233) must always be replaced by a new one ! • After having withdrawn the drift punch UT 2006, use the drift punch UT 2004 and, if necessary, the hammer UT 2111 to drive the breech lock pin (230) out of the barrel extension body (C1) (upper right part of Fig. 9.3.d). • After having withdrawn the drift punch UT 2004, the breech lock (221) can be taken out of its housing in the barrel extension body (C1) (lower part of Fig. 9.3.d). Take into account that the spring pin (233) is inside the body of the breech lock (221).

To reassemble, follow the above steps in reverse order, taking into account the following points : - Reinstall the breech lock (221) with its hole for the spring pin (233) at the lower side and with its upper inclined locking face at the front side. - If the previously used breech lock (221) is reinstalled again, it will not be necessary to carry out the adjustment of the headspace. - If the breech lock (221) should be replaced by a new one, first (before the adjustment of the headspace) install a new breech lock which is identical (same number) to the previous one. After having secured the new breech lock (221) into position by using the breech lock pin (230), carry out the adjustment of the headspace described in § 10.4. - Use the drift pin OREA 870 to install a new spring pin (233) (Fig. 9.3.e). Using the drift pin OREA 870 ensures a correct positioning of the spring pin (233).

- The breech lock pin (230) should not protrude after it has been reinstalled.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

B1 SY YY Y

SY YY Y

B1

X X X X YYYY UUUU

12 YY YY

9m m

U XU X

Upside down

U XU X

YY

YY

Upside down

C1

C1

Fig. 9.3.f - Marking a not marked barrel extension body (C1)

Fig. 9.3.g - Changing an existing mark on the barrel extension body (C1)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.3.

BARREL EXTENSION GROUP [ 3 ] (continued)

9.3.3.

Marking the barrel extension body (C1) The bottom of the barrel extension body (C1) must be marked with the last four digits of the serial number of the machine gun in order to ensure that the barrel extension assembly (200) is not interchanged between different machine guns when carrying out the field stripping procedure (also refer to the beginning of § 7.2). It is assumed that the marking of the barrel extension body (C1) has been asked during another procedure (normally during the adjustment of the headspace described in § 10.4).

Requirements : • Marking tools a.

The barrel extension body (C1) is not marked yet (Fig. 9.3.f) Mark the bottom of the barrel extension body (C1) with the last four digits ‘YYYY’ of the serial number of the machine gun. The serial number of the machine gun has been marked in the front part of the upper rear plate of the receiver frame (B1) (‘SYYYY’ on Fig 9.3.f). The mark should start at 129 mm from the front side of the barrel extension body (C1). It is recommended that the marked digits have a height of 5 mm and that there is a distance of 2.5 mm between the digits and the outside edge of the barrel extension body (C1).

b.

The barrel extension body (C1) has been marked but the marked digits are not correct anymore (Fig. 9.3.g) • Using the mark ‘I’, make a cross on each of the (wrong) four digits ‘UUUU’ presently marked on the bottom of the barrel extension body (C1). • Mark the correct last four digits ‘YYYY’ of the serial number of the machine gun after the previous number combination. The serial number of the machine gun has been marked in the front part of the upper rear plate of the receiver frame (B1) (‘SYYYY’ on Fig 9.3.g). It is recommended that the marked digits have a height of 5 mm and that there is a distance of 2.5 mm between the digits and the outside edge of the barrel extension body (C1).

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

f

482

483 481

410

c b

f

484

b d

a a

479

476 472

c

475

450

e

440

474 460

478

471 477

430

D2

D1

d

473

e

400

Fig. 9.4.a - Feed cover group [ 4 ]

3832

D1

482

.

.

.

UT 1803

B1

D1

483

B1

a

3831

482 UT 2004 Fig. 9.4.b - Removal of the feed cover (D1)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.4.

FEED COVER GROUP [ 4 ] (Fig. 9.4.a)

9.4.1.

Removal and reinstallation of the feed cover (D1) Please note that, during the following procedure, the cover pawl (3831) and its spring (3832) (parts of the receiver group [ 2 ] (also refer to § 9.2.15)) will also be released.

Requirements : • • • •

UT 1803 (Half-round nose pliers) UT 2004 (Drift punch, dia. 5 mm, lg 40 mm) UT 2111 (Hammer 250 g) UT 2203 (Feeler gauge)

• Using the pliers UT 1803, unbend the split pin (483) and then pull it out of the left end of the feed cover axis pin (482) (left part of Fig. 9.4.b). • Using the drift punch UT 2004 and the hammer UT 2111 from the left side, drive out the feed cover axis pin (482) (middle part of Fig. 9.4.b). • Withdraw the drift punch UT 2004. • Taking into account that it is subjected to the force of the cover pawl (3831) and its spring (3832), open the feed cover (D1) by turning its latch shaft (440) and then lift it up and off the receiver frame (B1) (middle part of Fig. 9.4.b). • Take the cover pawl (3831) and its spring (3832) out of their housing in the receiver frame (B1) (right part of Fig. 9.4.b). To reassemble, follow the above steps in reverse order, taking into account the following points : - When reinstalling the cover pawl (3831), its notch (a) should be facing outwards. - When fitting the feed cover axis pin (482), from the right side, back into position, a light pressure will be required on the feed cover (D1), against the force of the cover pawl spring (3832), in order to correctly align the pin holes. Please note that this light pressure can also be obtained by closing the feed cover (D1) before fitting the feed cover axis pin (482) back into position.

- After having reinstalled and closed the feed cover (D1), use the feeler gauge UT 2203 in order to check if the clearance between the feed cover latch (479) and the upper plate of the receiver frame (B1) does not exceed 0.2 mm (Fig. 9.4.c). If the clearance exceeds 0.2 mm, first check if the feed cover latch (479) is installed correctly. If there is no apparent problem, the feed cover latch should be replaced by a new one.

- After having reinstalled the split pin (483), lock it by bending its 2 extremities.

UT 2203

479 D1 B1 Fig. 9.4.c - Checking the clearance between the feed cover latch (479) and the upper plate of the receiver frame (B1) Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

UT 1803

.

D2

410

b a

410

c a

473 471 475 471 D2 d c

474 475

b

a

410 Fig. 9.4.d - Removal of the belt feed lever (471) and the belt feed slide assembly (D2)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.4.

FEED COVER GROUP [ 4 ] (continued)

9.4.2.

Removal and reinstallation of the belt feed lever (471) and the belt feed slide assembly (D2) This procedure applies to the (standard) left-hand fed MI.50 M2HB QCB machine gun. In case of a right-hand fed machine gun, refer to § 12.1. Please note that, for this operation, it is not necessary to remove the feed cover (D1).

Requirements : • UT 1803 (Half-round nose pliers) • UT 1903 (Screwdriver 3 x 75 mm) • Open the feed cover (D1) by turning its latch shaft (440). • Using the pliers UT 1803, pull the retaining spring (473) out of its hole in the mounting pin (a) of the feed cover body (410) (upper left part of Fig. 9.4.d). • Align the front end of the belt feed lever (471) with the open central part of the T-notch (b) in the feed cover body (410) (upper right part of Fig. 9.4.d). • Slightly slide the belt feed lever (471) off the mounting pin (a) of the feed cover body (410) until the front end of the lever just comes out of the notch (c) in the belt feed slide assembly (D2) (upper right part of Fig. 9.4.d). Do not slide the belt feed lever (471) so far off the mounting pin (a) that its pin (475) (see further) is released !

• Slide the belt feed slide assembly (D2) out of its housing in the feed cover body (410). • Slowly slide the belt feed lever (471) further off the mounting pin (a) until the belt feed lever pin (475) is just not released (upper right part of Fig. 9.4.d). Please note that the belt feed lever pin (475) is subjected to the pressure of the spring (474).

• While holding back the belt feed lever pin (475) with a finger, continue sliding the belt feed lever (471) off the mounting pin (a) until the pin is released and then take the pin, together with the spring (474), out of their housing (d) in the belt feed lever (lower part of Fig. 9.4.d). • Slide the belt feed lever (471) completely off the mounting pin (a) (lower part of Fig. 9.4.d). To reassemble, follow the above steps in reverse order, taking into account the following points : - Ensure that the belt feed lever (471) is oriented correctly (refer to Fig. 9.4.d). - Lightly lubricate the belt feed lever pin (475) and the spring (474) before reinstalling them. - Fit the belt feed lever pin (475) into the spring (474) and then insert this assembly, with the spring first, into its housing (d) in the belt feed lever (471) just before this housing is at the same height of the edge of the feed cover body (410) when sliding the belt feed lever back onto the mounting pin (a). Hold the belt feed lever pin (475) in place with the screwdriver UT 1903.

- Just after the belt feed lever pin (475) has been held back, insert the belt feed slide assembly (D2) (oriented as shown in Fig. 9.4.d) into its housing in the feed cover body (410) and then align its notch (c) with the front end of the belt feed lever (471). - Ensure that the front end of the belt feed lever (471) correctly engages into the notch (c) of the belt feed slide assembly (D2) and check if both the belt feed lever and the belt feed slide assembly can operate smoothly. Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

430

477

.

UT 2012

477

.

450

D2

478

.

430

460

Fig. 9.4.e - Disassembling the belt feed slide assembly (D2)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.4.

FEED COVER GROUP [ 4 ] (continued)

9.4.3.

Disassembling and reassembling the belt feed slide assembly (D2) This procedure applies to the (standard) left-hand fed MI.50 M2HB QCB machine gun. In case of a right-hand fed machine gun, refer to § 12.1. Please note that, for this operation, it is not necessary to remove the feed cover (D1).

Requirements : • • • •

UT 1803 (Half-round nose pliers) UT 1903 (Screwdriver 3 x 75 mm) UT 2012 (Drift punch, dia. 3.5 mm, lg 27 mm) UT 2111 (Hammer 250 g)

• Open the feed cover (D1) by turning its latch shaft (440). • Remove the belt feed slide assembly (D2) as described in § 9.4.2. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the belt feed slide assembly (D2) can be fixed into a vice. When fixing the belt feed slide assembly (D2) into a vice, use special clamps or a rag to avoid scratches.

• Using the drift punch UT 2012 and the hammer UT 2111, drive out the pin (460) (left part of Fig. 9.4.e). • While firmly holding the assembly formed by the belt feed pawl (430) and its arm (477) in position with a finger, withdraw the drift punch UT 2012. • Gently release and then remove the assembly formed by the belt feed pawl (430) and its arm (477) together with the pawl spring (478) from the belt feed slide (450) (middle part of Fig. 9.4.e). • Separate the belt feed pawl (430) and its arm (477) (right part of Fig. 9.4.e). To reassemble, follow the above steps in reverse order, taking into account the following points : - The wider extremity of the L-shaped pawl spring (478) should correctly engage its housing in the belt feed pawl (430) while the other extremity of the spring should correctly fit into the notch provided in the belt feed slide (450). On the other hand, the L-shaped pawl spring (478) should be oriented so that its body is at the side of the belt feed pawl arm (477). - The pin (460) should not protrude after it has been reinstalled.

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

472

. .

a 472

410

410 b

c

UT 1913

b

Fig. 9.4.f - Removal of the feed cover latch spring (472)

UT 1913 476 c

.

b

a

.

a

. 410

476

b

d

410

Fig. 9.4.g - Removal of the extractor spring (476)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.4.

FEED COVER GROUP [ 4 ] (continued)

9.4.4.

Removal and reinstallation of the feed cover latch spring (472) Please note that, for this operation, it is not necessary to remove the feed cover (D1).

Requirements : • UT 1803 (Half-round nose pliers) • UT 1903 (Screwdriver 3 x 75 mm) • UT 1913 (Screwdriver 5.5 x 150 mm) • Open the feed cover (D1) by turning its latch shaft (440). • Remove the belt feed lever (471) and the belt feed slide assembly (D2) as described in § 9.4.2. • Using the screwdriver UT 1913, disengage the front claw (a) of the feed cover latch spring (472) from the groove (b) in the feed cover body (410) (left part of Fig. 9.4.f). • Move the feed cover latch spring (472) forwards so that it can be released from the mounting pin (c) of the feed cover body (410) and then remove it (right part of Fig. 9.4.f). To reassemble, follow the above steps in reverse order, taking into account that the front claw (a) of the feed cover latch spring (472) should correctly engage the groove (b) in the feed cover body (410).

9.4.5.

Removal and reinstallation of the extractor spring (476) Please note that, for this operation, it is not necessary to remove the feed cover (D1).

Requirements : • UT 1803 (Half-round nose pliers) • UT 1903 (Screwdriver 3 x 75 mm) • UT 1913 (Screwdriver 5.5 x 150 mm) • Open the feed cover (D1) by turning its latch shaft (440). • Remove the belt feed lever (471) and the belt feed slide assembly (D2) as described in § 9.4.2. • Remove the feed cover latch spring (472) as described in § 9.4.4. • Using the screwdriver UT 1913, disengage the rear lug (a) of the extractor spring (476) from the notch (b) in the extractor guide cam (c) of the feed cover body (410) (left part of Fig. 9.4.g). • Disengage the front end of the extractor spring (476) from the mounting pin (d) of the feed cover body (410) and then remove the extractor spring (right part of Fig. 9.4.g). To reassemble, follow the above steps in reverse order, taking into account that the rear end of the extractor spring (476) should be depressed in order to enable its rear lug (a) to correctly engage the notch (b) in the extractor guide cam (c) of the feed cover body (410).

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

484

481

a

472

UT 1803

.

440

479

.

484

440

410

Fig. 9.4.h - Removal of the feed cover latch shaft (440) and the feed cover latch (479)

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

9.4.

FEED COVER GROUP [ 4 ] (continued)

9.4.6.

Removal and reinstallation of the feed cover latch shaft (440) and the feed cover latch (479) This procedure applies to the (standard) case that the feed cover latch shaft (440) is installed at the left side of the MI.50 M2HB QCB machine gun. In case of a right mounting, refer to § 12.3. Please note that, for this operation, it is not necessary to remove the feed cover (D1).

Requirements : • UT 1803 (Half-round nose pliers) • Open the feed cover (D1) by turning its latch shaft (440). • Using the pliers UT 1803, unbend the split pin (484) and then pull it out of the right end of the feed cover latch shaft (440) (left part of Fig. 9.4.h). • Taking care not to lose the washer (481) and taking into account that the feed cover latch (479) will be released, pull the feed cover latch shaft (440) out of the left side of the feed cover body (410) (right part of Fig. 9.4.h). To reassemble, follow the above steps in reverse order, taking into account the following points : - Ensure that the feed cover latch (479) is oriented correctly (refer to Fig. 9.4.h). - Ensure that the pointed front part of the feed cover latch (479) fits correctly between the rear end of its spring (472) and the feed cover body (410). - When fitting the feed cover latch shaft (440), from the left side, back into position, a light pressure will be required on the feed cover latch (479), against the force of its spring (472), in order to correctly align the pin holes. - Before reinstalling the split pin (484), fit the washer (481), in the notch (a) of the feed cover body (410), onto the right end of the feed cover latch shaft (440). - After having reinstalled the split pin (484), lock it by bending its 2 extremities.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

870

831 865 863 823

c

e d

840 867

844

862

f

843

E1

e d

820

f

868

842

c

864 E2

866

a

853

850

861 852 b b a

E3

810 800

Fig. 9.5.a - Bolt group [ 5 ] The bolt assembly (810) may never be interchanged between different machine guns : it must always be used with the same gun (and especially with the same barrel extension assembly (200)) ! For more information about the marks used to ensure this requirement, refer to § 7.2 and to § 9.5.9. For the removal and the reinstallation of the driving spring assembly (870), proceed as described for ‘field stripping’ in § 7.1 and § 7.2.

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

9.5.

BOLT GROUP [ 5 ] (Fig. 9.5.a)

9.5.1.

Removal and reinstallation of the extractor/ejector assembly (840) • Remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1. • The extractor/ejector assembly (840) can simply be removed by first raising it to the vertical position and then taking it out of its housing in the left side of the bolt (820) (Fig. 9.5.b). To reassemble, follow the above steps in reverse order, taking into account the following points : - The hinge pin (a) of the extractor/ejector assembly (840), which should be pushed fully into the bolt (820), is also used to lock the bolt switch (831) into position. - After its reinstallation, check if the extractor/ejector assembly (840) can move freely to the horizontal position.

9.5.2.

Removal and reinstallation of the bolt switch (831) This procedure applies to the (standard) left-hand fed MI.50 M2HB QCB machine gun. In case of a right-hand fed machine gun, refer to § 12.1.

• Remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1. • Remove the extractor/ejector assembly (840) as described in § 9.5.1. • The bolt switch (831) can now simply be lifted up and out of the bolt (820) (Fig. 9.5.c). To reassemble, follow the above steps in reverse order, taking into account that the orientation of the bolt switch (831) is different for a left-hand or a right-hand fed machine gun (also refer to § 2.2.5 and/or to § 12.1) and that the pin (823) should correctly engage the corresponding hole in the bolt switch.

831

.

831

820

820 840

. 823

a

831

Fig. 9.5.b - Removal of the extractor/ejector assembly (840)

Fig. 9.5.c - Removal of the bolt switch (831) Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

.

865

820

. 866 Fig. 9.5.d - Removal of the cocking lever (865) and its pin (866)

867 867

.

820

868 820

820

.

868

Fig. 9.5.e - Removal of the firing pin spring stop (868) and the lock (867)

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

9.5.

BOLT GROUP [ 5 ] (continued)

9.5.3.

Removal and reinstallation of the cocking lever (865) and its pin (866) Requirements : • Drift punch or similar tool • Remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1. • If not already done, pull the cocking lever (865) completely rearwards and then, with the tip of a screwdriver or a similar tool, push down on the sear (863) in order to release the firing pin (861) (also refer to § 7.1). • Using a pointed tool such as a drift punch from the right side, push the cocking lever pin (866) out of the left side of the bolt (820) (Fig. 9.5.d). • Lift the cocking lever (865) up and out of its housing in the bolt (820) (Fig. 9.5.d). To reassemble, follow the above steps in reverse order, taking into account the following points : - The cocking lever (865) should be fitted into its housing in the bolt (820) while holding it as shown in Fig. 9.5.d. - After having reinstalled the cocking lever (865), check if the bolt assembly (810) operates correctly : first cock the firing pin (861) by pushing the cocking lever forwards, move the upper end of the cocking lever back rearwards and then check if the firing pin is correctly released when pushing down on the sear (863).

9.5.4.

Removal and reinstallation of the firing pin spring stop (868) and the lock (867) Requirements : • Drift punch or similar tool • When not using tip of cocking lever, UT 1903 (Screwdriver 3 x 75 mm) • Remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1. • Remove the cocking lever (865) as described in § 9.5.3. • Using the screwdriver UT 1903 (or the tip of the cocking lever (865)), release the rear end of the lock (867) from its groove in the bolt (820) (Fig. 9.5.e). • Using the screwdriver UT 1903 (or the tip of the cocking lever (865)), disengage the front end of the lock (867) from the upper end of the firing pin spring stop (868) and then lift the lock up and out of the bolt (820) (Fig. 9.5.e). • Take the firing pin spring stop (868) out of the bottom of the bolt (820) (Fig. 9.5.e). To reassemble, follow the above steps in reverse order, taking into account the following points : - The firing pin spring stop (868) must be reinserted so that it passes through the groove in the firing pin extension body (E3) and behind the rear coil of the firing pin spring (852). - Reinstall the lock (867) with its concave side facing upwards, fit its fork-shaped front end onto the recess in the upper end of the firing pin spring stop (868) and engage its rear end into the corresponding groove in the bolt (820). - After having reinstalled the cocking lever (865), check if the bolt assembly (810) operates correctly as described in § 9.5.3.

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

820

.

.

863

820

864 863

.

. b

a

864

862

Fig. 9.5.f - Removal of the sear slide (864), the sear (863) and its spring (862)

820

.

E2 Fig. 9.5.g - Removal of the firing pin assembly (E2)

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

9.5.

BOLT GROUP [ 5 ] (continued)

9.5.5.

Removal and reinstallation of the sear slide (864), the sear (863) and its spring (862) Requirements : • Drift punch or similar tool • When not using tip of cocking lever, UT 1903 (Screwdriver 3 x 75 mm) • Remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1. • Remove the cocking lever (865) as described in § 9.5.3. • Remove the firing pin spring stop (868) and the lock (867) as described in § 9.5.4. • Using the tip of a screwdriver or a similar tool, push down on the sear (863) until its lug (a) has completely disengaged the notch (b) of the sear slide (864) and then, from the left side, pull the sear slide out of its housing in the rear side of the bolt (820) (Fig. 9.5.f). • Release the sear (863). • Lift the sear (863) and its spring (862) up and out of their housing at the rear side of the bolt (820) (right part of Fig. 9.5.f). To reassemble, follow the above steps in reverse order, taking into account the following points : - The sear (863) should be reinstalled with its lug (a) facing rearwards. - In order to facilitate the reinstallation of the sear spring (862), it is recommended to hold it by fitting the tip of a screwdriver (or the tip of the cocking lever (865)) between its coils. - After having reinstalled the cocking lever (865), check if the bolt assembly (810) operates correctly as described in § 9.5.3.

9.5.6.

Removal and reinstallation of the firing pin assembly (E2) Requirements : • Drift punch or similar tool • When not using tip of cocking lever, UT 1903 (Screwdriver 3 x 75 mm) • Remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1. • Remove the cocking lever (865) as described in § 9.5.3. • Remove the firing pin spring stop (868) and the lock (867) as described in § 9.5.4. • Remove the sear (863) as described in § 9.5.5. • The firing pin assembly (E2) can now simply be pulled out of its housing at the rear side of the bolt (820) (Fig. 9.5.g). To reassemble, follow the above steps in reverse order, taking into account the following points : - If desired, the firing pin assembly (E2) can be disassembled and reassembled as described in § 9.5.8. - The firing pin assembly (E2) should be reinstalled so that the flat part of its rear end is facing downwards. - After having reinstalled the cocking lever (865), check if the bolt assembly (810) operates correctly as described in § 9.5.3.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

E1

UT 2008

.

E1

842 843

844

842

844 Fig. 9.5.h - Disassembling the extractor/ejector assembly (840)

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

9.5.

BOLT GROUP [ 5 ] (continued)

9.5.7.

Disassembling and reassembling the extractor/ejector assembly (840) Requirements : • OREA 722 (Center punch, round-end) • UT 2008 (Drift punch, dia. 1.9 mm, lg 25 mm) • UT 2111 (Hammer 250 g) • Remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1. • Remove the extractor/ejector assembly (840) as described in § 9.5.1. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the extractor/ejector assembly (840) can be fixed into a vice. When fixing the extractor/ejector assembly (840) into a vice, fix it by the body of the extractor (E1) and use special clamps or a rag to avoid scratches.

• Using the drift punch UT 2008 and the hammer UT 2111 from the left side, drive out the pin (844) (left part of Fig. 9.5.h). Take into account that the left extremity of the pin (844) has been staked.

• While holding the ejector (842) in position with a finger, withdraw the drift punch UT 2008. • Gently release and then remove the ejector (842) together with its spring (843) out of their housing in the extractor (E1) (right part of Fig. 9.5.h). To reassemble, follow the above steps in reverse order, taking into account the following points : - The ejector spring (843) should fit into its housing in the extractor (E1) with its unbent extremity first. - After its reinstallation, secure the pin (844) by staking its left extremity by using the center punch OREA 722 and the hammer UT 2111.

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MI.50 M2HB QCB machine gun

852

UT 2012

850

.

861 850 OREA 269 853

E3

. 852 Fig. 9.5.i - Disassembling the firing pin assembly (E2)

Maintenance manual

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MI.50 M2HB QCB machine gun

9.5.

BOLT GROUP [ 5 ] (continued)

9.5.8.

Disassembling and reassembling the firing pin assembly (E2) Requirements : • • • •

OREA 269 (Rod, firing pin spring) UT 2012 (Drift punch, dia. 3.5 mm, lg 27 mm) Drift punch or similar tool When not using tip of cocking lever, UT 1903 (Screwdriver 3 x 75 mm)

• Remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1. • Remove the firing pin assembly (E2) as described in § 9.5.6. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the firing pin assembly (E2) can be fixed into a vice. When fixing the firing pin assembly (E2) into a vice, fix it by the firing pin extension (850) and use special clamps or a rag to avoid scratches.

• Disengage the firing pin (861) from the front end of the firing pin extension (850) (upper left part of Fig. 9.5.i). • Fit the OREA 269 onto the front end of the firing pin extension (850) in order to compress the firing pin spring (852) and to release the pressure on the pin (853) (upper right part of Fig. 9.5.i). • Using the drift punch UT 2012, drive out the pin (853) (upper right part of Fig. 9.5.i). • Remove the OREA 269 and then take the firing pin spring (852) out of the firing pin extension body (E3) (lower part of Fig. 9.5.i). To reassemble, follow the above steps in reverse order, taking into account that the pin (853) should not protrude after it has been reinstalled.

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MI.50 M2HB QCB machine gun

B1

SY

SY

YY

YY

Y

Y

B1

ZZ

ZZ

221

221

C1

C1

YY YYZZ

YY YY U XU XU XU X -V XV X

20

5m m

820 Fig. 9.5.j - Marking a not marked bolt (820)

YYYY XXXX XX UUUU-VV-ZZ -ZZ

820 Fig. 9.5.k - Changing an existing mark on the bolt (820)

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MI.50 M2HB QCB machine gun

9.5.

BOLT GROUP [ 5 ] (continued)

9.5.9.

Marking the bolt (820) The upper front part of the bolt (820) must be marked with the last four digits of the serial number of the machine gun as well as the number of the presently used breech lock (221) in order to ensure that the bolt assembly (810) is not interchanged between different machine guns when carrying out the field stripping procedure (also refer to the beginning of § 7.2). It is assumed that the marking of the bolt (820) has been asked during another procedure (normally during the adjustment of the headspace described in § 10.4).

Requirements : • Marking tools a.

The bolt (820) is not marked yet (Fig. 9.5.j) Mark the upper front part of the bolt (820) with the number combination ‘YYYY-ZZ’ where ‘YYYY’ represents the last four digits of the serial number of the machine gun and ‘ZZ’ represents the number of the breech lock (221) presently installed in the barrel extension body (C1). The serial number of the machine gun has been marked in the front part of the upper rear plate of the receiver frame (B1) (‘SYYYY’ on Fig 9.5.j). The number of the breech lock (221) has been marked in its cavity (‘ZZ’ on Fig. 9.5.j). The mark should start at 205 mm from the rear side of the bolt (820). It is recommended that the marked digits have a height of 3 mm and that there is a distance of 6 mm between the digits and the outside edge of the bolt (820).

b.

The bolt (820) has been marked but the marked number combination is not correct anymore (Fig. 9.5.k) If the ‘serial number’-part of the number combination is not correct anymore, proceed as follows : • Using the mark ‘I’, make a cross on each of the (wrong) four digits ‘UUUU’ presently marked on the upper front part of the bolt (820). • Mark the correct last four digits ‘YYYY’ of the serial number of the machine gun at the right side of the previous number combination. The serial number of the machine gun has been marked in the front part of the upper rear plate of the receiver frame (B1) (‘SYYYY’ on Fig 9.5.k). It is recommended that the marked digits have a height of 3 mm and that there is a distance of 1.5 mm between the digits and the outside edge of the bolt (820).

If the ‘breech lock number’-part of the number combination is not correct anymore, proceed as follows : • Using the mark ‘I’, make a cross on each of the (wrong) two digits ‘VV’ presently marked on the upper front part of the bolt (820). • Starting with a hyphen ‘-’, mark the correct two digits ‘ZZ’ representing the number of the presently used breech lock (221) after the previous number combination. The number of the breech lock (221) has been marked in its cavity (‘ZZ’ on Fig. 9.5.k). It is recommended that the marked digits have a height of 3 mm and that there is a distance of 6 mm between the digits and the outside edge of the bolt (820).

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FN HERSTAL

MI.50 M2HB QCB machine gun

520

e

523

528

e

525

529 d

526

524

d

527

522

548 a

545

521

c

551

547

b

546

a

510

542

b

543

c

541

544 549 500

Fig. 9.6.a - Rear sight group [ 6 ] (*)

After any intervention on the rear sight group [ 6 ], the firing precision of the machine gun should be checked and, if necessary, adjusted as described in § 10.1 and § 10.2.

(*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, refer to § 13.1.7.

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MI.50 M2HB QCB machine gun

9.6.

REAR SIGHT GROUP [ 6 ] (*) (Fig. 9.6.a)

9.6.1.

Removal and reinstallation of the rear sight assembly (500) Requirements : • • • • •

UT 1910 (Screwdriver 10 x 200 mm) UT 2030 (Center punch, dia. 6 mm) UT 2111 (Hammer 250 g) Requirements of § 10.2 Requirements of § 10.5

• Remove the back plate assembly (600) as described for ‘field stripping’ in § 7.1. • Using the screwdriver UT 1910 and taking into account that it also secures the trigger bar stop assembly (B5) (also refer to § 9.2.13), take out the screw (3654) which secures the rear part of the rear sight assembly (500) to the receiver frame (B1). Take into account that the head of the screw (3654) has been staked.

• Using the screwdriver UT 1910, take out the 2 screws (551) which secure the front part of the rear sight assembly (500) to the receiver frame (B1) (left part of Fig. 9.6.b). Take into account that the heads of the screws (551) have been staked.

• Lift the rear sight assembly (500) up and off the receiver frame (B1) (right part of Fig. 9.6.b). To reassemble, follow the above steps in reverse order, taking into account the following points : - Ensure that the positioning pins (a) underneath the rear sight assembly (500) fit correctly into the corresponding holes (b) provided in the upper plate of the receiver frame (B1). - Reinstall the trigger bar stop assembly (B5) by proceeding as described in ‘10.5. Adjustment of the timing’. - After their reinstallation, secure the screws (3654) and (551) by staking their heads by using the center punch UT 2030 and the hammer UT 2111.

500

B1 UT 1910

551

.

a b

b

500 B1 Fig. 9.6.b - Removal of the rear sight assembly (500) After any intervention on the trigger bar stop assembly (B5), the timing of the machine gun should be checked and, if necessary, adjusted as described in § 10.5. Maintenance manual

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MI.50 M2HB QCB machine gun

UT 2005 544

.

543

542 541

545

541

.

542

Fig. 9.6.c - Removal of the rear sight windage knob (541)

520

520 510 549

545

510

. 546

545 UT 1913

546

Fig. 9.6.d - Removal of the rear sight windage adjusting screw (545) and the rear sight leaf assembly (520)

Maintenance manual

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MI.50 M2HB QCB machine gun

9.6.

REAR SIGHT GROUP [ 6 ] (*) (continued)

9.6.2.

Removal and reinstallation of the rear sight leaf assembly (520), the rear sight windage knob (541) and the rear sight windage adjusting screw (545) Please note that, for this operation, it is not necessary to remove the rear sight assembly (500).

Requirements : • • • •

UT 1913 (Screwdriver 5.5 x 150 mm) UT 2005 (Drift punch, dia. 1.4 mm, lg 15 mm) UT 2111 (Hammer 250 g) Requirements of § 10.2

NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the machine gun can be fixed into a vice. When fixing the machine gun into a vice, use special clamps or a rag to avoid scratches.

• Using the drift punch UT 2005 and the hammer UT 2111, drive out the pin (542) (left part of Fig. 9.6.c). NOTE : Once it has been removed, the pin (542) must always be replaced by a new one ! • After having withdrawn the drift punch UT 2005 and taking into account that the windage click plunger (543) and its spring (544) will be released, pull the rear sight windage knob (541) off the left end of the rear sight windage adjusting screw (545) (right part of Fig. 9.6.c). • Using the screwdriver UT 1913 from the right side and taking into account that both the rear sight leaf assembly (520) and the rear sight leaf stop (546) will be released, completely unscrew the rear sight windage adjusting screw (545) out of the rear sight base (510) (left part of Fig. 9.6.d). During this operation, it is recommended to push down slightly on the rear sight leaf assembly (520) as the latter is subjected to the force of the rear sight base spring (549).

• Lift the rear sight leaf assembly (520) up and off the rear sight base (510) (right part of Fig. 9.6.d). • If it did not come out yet, take the rear sight leaf stop (546) out of its hole in the right side of the rear sight base (510). To reassemble, follow the above steps in reverse order, taking into account the following points : - The rear sight leaf stop (546) should be fitted, from the outside and with its narrower end first, into its hole in the right side of the rear sight base (510). - When fitting the rear sight leaf assembly (520) back into position, ensure that its graduations are facing rearwards. - When screwing the rear sight windage adjusting screw (545), from the right side, back into position, a light downward pressure will be required on the rear sight leaf assembly (520), against the force of the rear sight base spring (549), in order to correctly align the screw holes. Ensure that the rear sight windage adjusting screw (545) fits correctly and completely into the hole in the left side of the rear sight base (510).

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MI.50 M2HB QCB machine gun

UT 1903 510 548 547

548

Fig. 9.6.e - Removal of the rear sight windage scale (547)

UT 2111

UT 2004 549

.

510

Fig. 9.6.f - Removal of the rear sight base spring (549)

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

9.6.

REAR SIGHT GROUP [ 6 ] (*) (continued)

9.6.2.

Removal and reinstallation of the rear sight leaf assembly (520), the rear sight windage knob (541) and the rear sight windage adjusting screw (545) (continued) - When reinstalling the windage click plunger (543), first fit it onto its spring (544) and then insert this assembly, slightly lubricated and with the free extremity of the spring first, into the hole in the right side of the rear sight windage knob (541). - If it is difficult to insert the pin (542), use the drift punch UT 2005 to assist to align the holes in the rear sight windage knob (541) with the corresponding hole in the left end of the rear sight windage adjusting screw (545). - The pin (542) should not protrude after it has been reinstalled.

9.6.3.

Removal and reinstallation of the rear sight windage scale (547) Please note that, for this operation, it is not necessary to remove the rear sight assembly (500).

Requirements : • UT 1903 (Screwdriver 3 x 75 mm) • Requirements of § 10.2 • Using the screwdriver UT 1903, take out the 2 screws (548) which secure the rear sight windage scale (547) to the rear sight base (510) (Fig. 9.6.e). • Remove the rear sight windage scale (547) (Fig. 9.6.e). To reassemble, follow the above steps in reverse order.

9.6.4.

Removal and reinstallation of the rear sight base spring (549) Please note that, for this operation, it is not necessary to remove the rear sight assembly (500).

Requirements : • • • • • •

UT 1903 (Screwdriver 3 x 75 mm) UT 1913 (Screwdriver 5.5 x 150 mm) UT 2004 (Drift punch, dia. 5 mm, lg 40 mm) UT 2005 (Drift punch, dia. 1.4 mm, lg 15 mm) UT 2111 (Hammer 250 g) Requirements of § 10.2

• Remove the rear sight leaf assembly (520) as described in § 9.6.2. • Remove the rear sight windage scale (547) as described in § 9.6.3. • Using the drift punch UT 2004 and the hammer UT 2111, disengage the rear sight base spring (549) from its housing in the rear sight base (510) (Fig. 9.6.f). To reassemble, follow the above steps in reverse order taking into account that the rear sight base spring (549), which should be lightly lubricated before its reinstallation, should fit completely into its housing in the rear sight base (510).

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

522

521

OREA 798

525

524

523

.

529

525

528

Fig. 9.6.g - Removal of the rear sight slide elevating knob (523)

OREA 798

b 524

522

.

526

.

524 521

.

a b 522

527

524

521

527

Fig. 9.6.h - Removal of the rear sight slide (522), the rear sight slide elevating screw (524) and the rear sight half nut (527) Maintenance manual

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MI.50 M2HB QCB machine gun

9.6.

REAR SIGHT GROUP [ 6 ] (*) (continued)

9.6.5.

Disassembly and reassembly of the rear sight leaf assembly (520) Please note that, for this operation, it is not necessary to remove the rear sight assembly (500).

Requirements : • • • • • •

OREA 798 (Drift, 1.2 x 10 mm dia.) UT 1913 (Screwdriver 5.5 x 150 mm) UT 2005 (Drift punch, dia. 1.4 mm, lg 15 mm) UT 2030 (Center punch, dia. 6 mm) UT 2111 (Hammer 250 g) Requirements of § 10.2

• Remove the rear sight leaf assembly (520) as described in § 9.6.2. • Position, if it has not already been done, the rear sight slide (522) at its lowest position. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the rear sight leaf assembly (520) can be fixed into a vice. When fixing the rear sight leaf assembly (520) into a vice, use special clamps or a rag to avoid scratches.

• Using the drift punch OREA 798 and the hammer UT 2111, drive out the pin (525) (left part of Fig. 9.6.g). Take into account that both extremities of the pin (525) have been staked.

NOTE : Once it has been removed, the pin (525) must always be replaced by a new one ! • After having withdrawn the drift punch OREA 798 and taking into account that the elevating plunger (528) and its spring (529) will be released, pull the rear sight slide elevating knob (523) off the end of the corresponding screw (524) (right part of Fig. 9.6.g). • Take the elevating plunger (528) and its spring (529) out of their housing in the rear sight leaf (521) (right part of Fig. 9.6.g). • Using the drift punch OREA 798 and the hammer UT 2111, drive out the pin (526) (upper left part of Fig. 9.6.h). Take into account that both extremities of the pin (526) have been staked.

NOTE : Once it has been removed, the pin (526) must always be replaced by a new one ! • After having withdrawn the drift punch OREA 798, completely unscrew the rear sight slide elevating screw (524) and then take it out of its housing in the rear sight leaf (521) (upper right part of Fig. 9.6.h). • Using a tool like a drift punch from the left side and through the hole provided in the left side of the rear sight leaf (521), push the rear sight half nut (527) out of the right side of the rear sight leaf (upper right part of Fig. 9.6.h). • After having withdrawn the tool, the rear sight slide (522) can simply be separated from the rear sight leaf (521) (lower part of Fig. 9.6.h). Maintenance manual

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MI.50 M2HB QCB machine gun

THIS PAGE IS INTENTIONALLY BLANK

Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

9.6.

REAR SIGHT GROUP [ 6 ] (*) (continued)

9.6.5.

Disassembly and reassembly of the rear sight leaf assembly (520) (continued) To reassemble, follow the above steps in reverse order, taking into account the following points : - When fitting the rear sight slide (522) back into the rear sight leaf (521), ensure that its peep-hole (‘a’ on the lower part of Fig. 9.6.h) is facing rearwards and slide it towards the base of the rear sight leaf. - When inserting the rear sight half nut (527) from the right side, back into position, ensure that its teeth are at the right side and push it all the way into the rear sight slide (522). - When screwing the rear sight slide elevating screw (524) back into position, ensure that its thread correctly engages the teeth at the right side of the rear sight half nut (527) and never apply too much force. - The pin (526) can only be inserted back into position if the recess (‘b’ on the lower part of Fig. 9.6.h) in the rear sight slide elevating screw (524) is correctly aligned with the corresponding holes in the rear sight leaf (521). - After its reinstallation, secure the pin (526) by staking its 2 extremities by using the center punch UT 2030 and the hammer UT 2111. - When reinstalling the elevating plunger (528), first fit it into its spring (529) and then insert this assembly, slightly lubricated and with the free extremity of the spring first, into the hole in the rear sight leaf (521). - If it is difficult to insert the pin (525), use the drift punch OREA 798 to assist to align the holes in the rear sight slide elevating knob (523) with the corresponding hole in the end of the rear sight slide elevating screw (524). - After its reinstallation, secure the pin (525) by staking its 2 extremities by using the center punch UT 2030 and the hammer UT 2111.

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

913

912 b

c

910

b

962

a

G1 c

961

a

912

950

940 963

G2 d

930

922 d

921 925 920

924

900

Fig. 9.7.a - Buffer group [ 7 ]

G1

. 961

Fig. 9.7.b - Removal of the buffer body lock (961) Maintenance manual

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Catalog n° 3660084070

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MI.50 M2HB QCB machine gun

9.7.

BUFFER GROUP [ 7 ] (Fig. 9.7.a)

9.7.1.

Removal and reinstallation of the buffer body lock (961) Only remove the buffer body lock (961) when it is absolutely necessary !

Requirements : • UT 2111 (Hammer 250 g) • Drift punch or similar tool • Remove the buffer group (900) and then separate the assembly formed by the buffer body assembly (910) and the accelerator (962) and its pin (950) as described for ‘field stripping’ in § 7.1. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the buffer body assembly (910) can be fixed into a vice. When fixing the buffer body assembly (910) into a vice, use special clamps or a rag to avoid scratches.

• Using a drift punch and the hammer UT 2111, drive the buffer body lock (961) rearwards out of its housing in the right side of the buffer body (G1) (Fig. 9.7.b). It is possible that the buffer body lock (961) is held into position by staking. In such a case, first unbend the staking by using a tool such as a drift punch or a screwdriver.

To reassemble, follow the above steps in reverse order, taking into account the following points (Fig. 9.7.c) : - The buffer body lock (961) should be oriented so that its rear end comes slightly out of its housing (a) in the right side of the buffer body (G1) - Ensure that the buffer body lock (961) is inserted completely into its housing (a) in the right side of the buffer body (G1). - If, and only if, the (previous) buffer body lock (961) was held into position by staking, it (the new one) should also be secured by staking. In such a case, and using the center punch OREA 722 and the hammer UT 2111, stake material from the edge of the housing (a) into a not yet used notch of the buffer body lock (961). When staking, the same notch should never be used twice.

G1

. a 961 Fig. 9.7.c - Reinstallation of the buffer body lock (961) Maintenance manual

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MI.50 M2HB QCB machine gun

G1

. 950 962

950

962

Fig. 9.7.d - Removal of the accelerator (962)

G1

912 913

912

Fig. 9.7.e - Removal of the breech lock depressors (912)

a

OREA 848

913

912

a OREA 848 G1

Fig. 9.7.f - Reinstalling the breech lock depressors (912) by using the riveting clamp OREA 848 Maintenance manual

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MI.50 M2HB QCB machine gun

9.7.

BUFFER GROUP [ 7 ] (continued)

9.7.2.

Removal and reinstallation of the accelerator (962) Requirements : • Drift punch or similar tool • Remove the buffer group (900) and then separate the assembly formed by the buffer body assembly (910) and the accelerator (962) and its pin (950) as described for ‘field stripping’ in § 7.1. • Using a pointed tool such as a drift punch, push the accelerator pin (950) out of the buffer body (G1) and then release the accelerator (962) from the buffer body (Fig. 9.7.d). To reassemble, follow the above steps in reverse order, taking into account the following points : - The claws of the accelerator (962) should be at the front side and be pointing upwards. - The accelerator pin (950) should not protrude after it has been reinstalled.

9.7.3.

Removal and reinstallation of the breech lock depressors (912) As the breech lock depressors (912) are held into position by riveting, only remove them when it is absolutely necessary ! Always replace the breech lock depressors (912) as a pair.

Requirements : • • • •

OREA 848 (Riveting clamp depressor, breech, lock) UT 2004 (Drift punch, dia. 5 mm, lg 40 mm) UT 2111 (Hammer 250 g) Chisel or similar tool

• Remove the accelerator (962) as described in § 9.7.2. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the buffer body (G1) should be fixed into a vice. When fixing the buffer body (G1) into a vice, use special clamps or a rag to avoid scratches.

• Using a tool such as a chisel or a drift punch and the hammer UT 2111 from the outside, drive out the 2 rivets (913) and then take the breech lock depressors (912) out of their housings in the buffer body (G1) (Fig. 9.7.e). If it is difficult to release a breech lock depressor (912) from its housing, carefully use the hammer UT 2111.

To reassemble, follow the above steps in reverse order, taking into account the following points : - The rivets (913) should be inserted into their holes from the inside of the buffer body (G1). - Before riveting the rivets (913), secure their heads temporarily into position by using the riveting clamp OREA 848 as shown in Fig. 9.7.f. After having inserted the rivets (913), from the inside, into their holes, fit the riveting clamp OREA 848 into the large slot at the front side of the buffer body (G1) and then secure the tool into position by fitting its pin (a) through the mounting holes for the accelerator pin (950).

- The breech lock depressors (912) should be oriented so that the shouldered face on their front extremity is facing upwards (Fig. 9.7.f). - Rivet the outer extremities of the rivets (913) by using the drift punch UT 2004 and the hammer UT 2111 and then file off any protruding material. Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun a

b

. 963

920

930 963 OREA 574

Fig. 9.7.g - Using the tool OREA 574 to disassemble the barrel buffer assembly (920)

G2

921

925 963

921

UT 1184 G2

940 Fig. 9.7.h - Disassembled components of the barrel buffer assembly (920)

Fig. 9.7.i - Screwing the buffer piston assembly (G2) out of the barrel buffer tube (921)

c

930

930

924

UT 1803

924 925

921 1682

922 Fig. 9.7.j - Disassembled components of the buffer piston assembly (G2)

Fig. 9.7.k - Adjusting the distance between the buffer piston head (924) and the front nose of the buffer piston rod (930)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.7.

BUFFER GROUP [ 7 ] (continued)

9.7.4.

Disassembly and reassembly of the barrel buffer assembly (920) Requirements : • • • •

OREA 574 (Tool, MI.50 buffer spring) If required, UT 1184 (Open-end wrench 13/16 x 7/8”) If required, UT 1803 (Half-round nose pliers) If required, 1682 (Gauge, checking, piston head)

• Remove the barrel buffer assembly (920) as described for ‘field stripping’ in § 7.1. • Insert the barrel buffer assembly (920) into the tool OREA 574 so that the front nose of the buffer piston rod (930) engages the nose inside the tool (left part of Fig. 9.7.g). • While pushing down the lever (a) of the tool OREA 574 in order to compress the buffer spring (963), rotate the knob (b) of the tool by 90° (middle part of Fig. 9.7.g). As a result, the buffer piston rod (930) will be rotated so that its protruding retaining pins become aligned with the notches in the buffer spring guide (940).

• Slowly release the pressure on the lever (a) of the tool OREA 574 in order to release the pressure on the buffer spring (963) (right part of Fig. 9.7.g). During this operation, the buffer spring guide (940) will be released from the front end of the buffer piston rod (930).

• Take the disassembled barrel buffer assembly (920) out of the tool OREA 574. The barrel buffer assembly (920) is now disassembled into the buffer spring guide (940), the buffer spring (963) and the assembly formed by the buffer piston assembly (G2) and the barrel buffer tube (921) (Fig. 9.7.h).

• If required, disassemble the assembly formed by the buffer piston assembly (G2) and the barrel buffer tube (921) by proceeding as follows : - Fix the barrel buffer tube (921) by its rear flat ends into a vice (Fig. 9.7.i). - Using the wrench UT 1184 on the buffer tube cap (925), screw the buffer piston assembly (G2) out of the barrel buffer tube (921) (Fig. 9.7.i). - Using the pliers UT 1803, unbend the split pin (922) and then pull it out of the rear end of the buffer piston rod (930) (Fig. 9.7.j). - Unscrew the buffer piston head (924) and then slide the buffer tube cap (925) from the rear end of the buffer piston rod (930) (Fig. 9.7.j). To reassemble, follow the above steps in reverse order, taking into account the following points : - Before fitting the split pin (922) back into position, adjust the distance between the front side of the buffer piston head (924) and the front nose (c) of the buffer piston rod (930) by using the GO end of the piston head checking gauge (1682) as shown in Fig. 9.7.k. After this adjustment, ensure that the NO GO end of the piston head checking gauge (1682) cannot fit.

- After having reinstalled the split pin (922), lock it by bending its 2 extremities. - When reassembling the barrel buffer assembly (920) by using the tool OREA 574, ensure that the front nose of the buffer piston rod (930) correctly engages the nose inside the tool. Push down the lever of the tool in order to fit the buffer spring guide (940) onto the front end of the buffer piston rod (930) (the notches in the guide will pass over the protruding retaining pins of the rod). After that, turn the knob of the tool by 90° so that the guide is held back by the retaining pins of the rod when the lever of the tool is released.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

c e

735

723 e

722 a

726

730

719

728

b

721 711

717

713

717

d

719

717

c

719 715

716/1

728

a

727 735

H2 718

724 b

712 d

714

H1 700 725

Fig. 9.8.a - Cocking handle group [ 8 ]

B1

UT 1802

728 735

UT 1802 H1

726

727

728

735

Fig. 9.8.b - Removal of the 2 wires (735) Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.8.

COCKING HANDLE GROUP [ 8 ] (Fig. 9.8.a)

9.8.1.

Removal of the cocking handle assembly (H1) This procedure applies to the (standard) case that the cocking handle assembly (H1) is installed at the right side of the MI.50 M2HB QCB machine gun. In case of a left mounting, refer to § 12.2.

Requirements : • • • •

UT 1180 (Open-end wrench 5/8 x 3/4”) UT 1802 (Cutting pliers) UT 1803 (Half-round nose pliers) UT 1913 (Screwdriver 5.5 x 150 mm)

• Remove the barrel group [ 1 ], the back plate assembly (600), the driving spring assembly (870) and the moving parts as described for ‘field stripping’ in § 7.1. • Using the cutting pliers UT 1802 at the rear side of the cocking handle assembly (H1), remove the wire (735) from the (upper) screw (728) and the (lower) screw (727) (left part of Fig. 9.8.b). • Again using the cutting pliers UT 1802, remove the wire (735) between the other screw (728) and the cocking slide stud (726) (right part of Fig. 9.8.b). • Using the pliers UT 1803, unbend the 2 split pins (719) which secure the nuts (717) of the 2 shoulder bolts (718) and then pull the pins out of the right end of the shoulder bolts (left part of Fig. 9.8.c). • Using the wrench UT 1180, unscrew the nuts (717) from the 2 shoulder bolts (718) and then, from the inside of the receiver frame (B1), release and remove the 2 shoulder bolts (right part of Fig. 9.8.c). • Using the screwdriver UT 1913, take out the screw (727) and the 2 screws (728) and then release and remove the cocking handle assembly (H1) from the right side of the receiver frame (B1) (also refer to Fig. 9.8.b). Although they are of the same type, the screw (727) is shorter than the 2 screws (728).

UT 1803 719

B1 718

UT 1180 H1 H1

717

Fig. 9.8.c - Removal of the 2 shoulder bolts (718)

For the removal and the reinstallation of the bolt stud (725), proceed as described for ‘field stripping’ in § 7.1 and § 7.2.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

UT 1180

UT 1803 719

B1

718 H1 H1

717

UT 1808

B1 728

H1

728 727 735

735

726

Fig. 9.8.d - Reinstallation of the cocking handle assembly (H1)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.8.

COCKING HANDLE GROUP [ 8 ] (continued)

9.8.2.

Reinstallation of the cocking handle assembly (H1) (Fig. 9.8.d) This procedure applies to the (standard) case that the cocking handle assembly (H1) is installed at the right side of the MI.50 M2HB QCB machine gun. In case of a left mounting, refer to § 12.2.

Requirements : • • • •

UT 1180 (Open-end wrench 5/8 x 3/4”) UT 1803 (Half-round nose pliers) UT 1808 (Lock wire pliers) UT 1913 (Screwdriver 5.5 x 150 mm)

• Reinstall the cocking handle assembly (H1) onto the right side of the receiver frame (B1) and fix it by screwing the (shorter) screw (727) and the 2 (longer) screws (728) manually back into position. Please note that the (shorter) screw (727) is used at the lower rear side.

• From the inside of the receiver frame (B1), fit the 2 shoulder bolts (718) back into position. Ensure that the rectangular heads of the shoulder bolts (718) fit correctly into the corresponding recesses provided inside the receiver frame (B1), taking into account that both the recesses and the heads have chamfered edges which must be facing each other. Ensure that the right extremities of the 2 shoulder bolts (718) fit correctly into the corresponding holes in the cocking slide bracket (711).

• While holding the rectangular heads of the 2 shoulder bolts (718) in position with the fingers, screw a nut (717), with its grooves facing outwards, onto the right extremity of each shoulder bolt. • Using the wrench UT 1180, tighten the 2 nuts (717) onto the shoulder bolts (718). Ensure that, at the end of this operation, one of the grooves of the nuts (717) is perfectly aligned with the hole in the right end of the corresponding shoulder bolt (718).

• For each shoulder bolt (718) and using the pliers UT 1803, fit a split pin (719) into the aligned groove of the corresponding nut (717) and the hole in the right end of the bolt. • Using the pliers UT 1803, lock both split pins (719) by bending their 2 extremities. • Firmly tighten the screws (727) and (728) with the screwdriver UT 1913. • Using a wire (735) and the lock wire pliers UT 1808 at the rear side of the cocking handle assembly (H1), secure the (upper) screw (728) and the (lower) screw (727). The lockwire should be installed so that, when tension is applied to it, this results in a tightening (and not a loosening) effort on the screws.

• Again using a wire (735) and the lock wire pliers UT 1808, secure the other screw (728) and the cocking slide stud (726). The lockwire should be installed so that, when tension is applied to it, this results in a tightening (and not a loosening) effort on the screw and the stud.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

UT 1803 730 713

719

717 715

714

716/1

Fig. 9.8.e - Removal of the assembly formed by the cocking slide lever (713) and the cocking handle (730) as well as the cocking handle spring (716/1)

730

730

UT 1180

713

b

716/1 713

a 714

724

Fig. 9.8.f - Separating the cocking slide lever (713) and the cocking handle (730)

Fig. 9.8.g - Correct installation of the cocking handle spring (716/1) Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.8.

COCKING HANDLE GROUP [ 8 ] (continued)

9.8.3.

Removal and reinstallation of the cocking slide lever (713), the cocking handle (730) and the cocking handle spring (716/1) This procedure applies to the (standard) case that the cocking handle assembly (H1) is installed at the right side of the MI.50 M2HB QCB machine gun. In case of a left mounting, refer to § 12.2. Please note that, although the cocking handle assembly (H1) has been removed on the illustrations of this paragraph, it is not necessary to remove it for this operation.

Requirements : • • • •

UT 1180 (Open-end wrench 5/8 x 3/4”) UT 1803 (Half-round nose pliers) UT 2030 (Center punch, dia. 6 mm) UT 2111 (Hammer 250 g)

• Using the pliers UT 1803, unbend the split pin (719) which secures the nut (717) to the right end of the cocking slide lever stud (714) and then pull the pin out of the stud (Fig. 9.8.e). • Using the wrench UT 1180 and taking care not to lose the washer (715), unscrew the nut (717) from the right end of the cocking slide lever stud (714) (Fig. 9.8.e). • Taking into account that the cocking handle spring (716/1) will be released, slide the assembly formed by the cocking slide lever (713) and the cocking handle (730) as well as the cocking handle spring itself off the right end of the cocking slide lever stud (714) (Fig. 9.8.e). NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the assembly formed by the cocking slide lever (713) and the cocking handle (730) can be fixed into a vice. When fixing the assembly into a vice, use special clamps or a rag to avoid scratches.

• Using the wrench UT 1180, unscrew the cocking handle (730) from the cocking slide lever (713) (Fig. 9.8.f). Take into account that the threaded end of the cocking handle (730) has been staked.

To reassemble, follow the above steps in reverse order, taking into account the following points : - After having screwed and tightened the cocking handle (730) into the cocking slide lever (713), secure the handle by staking its threaded end by using the center punch UT 2030 and the hammer UT 2111. - When reinstalling the cocking handle spring (716/1), ensure that its loop (a) fits correctly onto the cocking slide stop pin (724) and that its bent extremity fits correctly into the hole (b) provided in the cocking slide lever (713) (Fig. 9.8.g). - When screwing the nut (717) back onto the cocking slide lever stud (714), do not forget the washer (715) and ensure that the grooves of the nut are facing outwards. - When the nut (717) has been screwed completely home, one of its grooves should be perfectly aligned with the hole in the right end of the cocking slide lever stud (714) in order to enable the installation of the split pin (719). - After having reinstalled the split pin (719), lock it by bending its 2 extremities. Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

714

UT 1910

UT 1180

724 712

712

Fig. 9.8.h - Removal of the cocking slide stop pin (724)

Fig. 9.8.i - Separating the cocking slide lever stud (714) and the cocking slide (712)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.8.

COCKING HANDLE GROUP [ 8 ] (continued)

9.8.4.

Removal/disassembly and reassembly/reinstallation of the cocking slide assembly (H2) This procedure applies to the (standard) case that the cocking handle assembly (H1) is installed at the right side of the MI.50 M2HB QCB machine gun. In case of a left mounting, refer to § 12.2.

Requirements : • • • • • • • •

UT 1180 (Open-end wrench 5/8 x 3/4”) UT 1802 (Cutting pliers) UT 1803 (Half-round nose pliers) UT 1808 (Lock wire pliers) UT 1910 (Screwdriver 10 x 200 mm) UT 1913 (Screwdriver 5.5 x 150 mm) UT 2030 (Center punch, dia. 6 mm) UT 2111 (Hammer 250 g)

• Remove the assembly formed by the cocking slide lever (713) and the cocking handle (730) as well as the cocking handle spring (716/1) as described in § 9.8.3. • Taking into account that the cocking slide assembly (H2) will be released, remove the remaining part of the cocking handle assembly (H1) as described in § 9.8.1. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the cocking slide assembly (H2) can be fixed into a vice. When fixing the cocking slide assembly (H2) into a vice, use special clamps or a rag to avoid scratches.

• Using the screwdriver UT 1910, unscrew the cocking slide stop pin (724) from the cocking slide (712) (Fig. 9.8.h). Take into account that the threaded end of the cocking slide stop pin (724) has been staked.

• Using the wrench UT 1180, unscrew the cocking slide lever stud (714) from the cocking slide (712) (Fig. 9.8.i). Take into account that the threaded end of the cocking slide lever stud (714) has been staked.

To reassemble, follow the above steps in reverse order, taking into account the following points : - After having screwed and tightened the cocking slide stop pin (724) and the cocking slide lever stud (714) into the cocking slide (712), secure them by staking their threaded end by using the center punch UT 2030 and the hammer UT 2111. - When fitting the cocking slide assembly (H2), from the left side, back into its slot in the cocking slide bracket (711), orient it so that the cocking slide lever stud (714) is at the rear side and is facing outwards. - Ensure that the V-notch on top of the cocking slide (712) is correctly engaged by the cocking slide plunger (721).

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

UT 1802 726

735

728

Fig. 9.8.j - Removal of the cocking slide stud (726)

723

.

711

H1

721

.

UT 2012

722 Fig. 9.8.k - Removal of the cocking slide plunger (721) and its spring (722)

Maintenance manual

- 206 2009 08 EN Change 2

Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.8.

COCKING HANDLE GROUP [ 8 ] (continued)

9.8.5.

Removal and reinstallation of the cocking slide stud (726) This procedure applies to the (standard) case that the cocking handle assembly (H1) is installed at the right side of the MI.50 M2HB QCB machine gun. In case of a left mounting, refer to § 12.2.

Requirements : • UT 1802 (Cutting pliers) • UT 1808 (Lock wire pliers) • UT 1910 (Screwdriver 10 x 200 mm) • Using the cutting pliers UT 1802, remove the wire (735) between the ‘front’ screw (728) and the cocking slide stud (726) (Fig. 9.8.j). • Using the screwdriver UT 1910, unscrew the cocking slide stud (726) from the cocking slide bracket (711) (Fig. 9.8.j). To reassemble, follow the above steps in reverse order, taking into account that the cocking slide stud (726) should correctly be secured together with the ‘front’ screw (728) by using a wire (735) and the lock wire pliers UT 1808.

9.8.6.

Removal and reinstallation of the cocking slide plunger (721) and its spring (722) This procedure applies to the (standard) case that the cocking handle assembly (H1) is installed at the right side of the MI.50 M2HB QCB machine gun. In case of a left mounting, refer to § 12.2.

Requirements : • • • • • • •

UT 1180 (Open-end wrench 5/8 x 3/4”) UT 1802 (Cutting pliers) UT 1803 (Half-round nose pliers) UT 1808 (Lock wire pliers) UT 1913 (Screwdriver 5.5 x 150 mm) UT 2012 (Drift punch, dia. 3.5 mm, lg 27 mm) UT 2111 (Hammer 250 g)

• Remove the cocking handle assembly (H1) as described in § 9.8.1. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the cocking handle assembly (H1) can be fixed into a vice. When fixing the cocking handle assembly (H1) into a vice, use special clamps or a rag to avoid scratches.

• Using the drift punch UT 2012 and the hammer UT 2111, drive out the pin (723) (left part of Fig. 9.8.k). • While holding the cocking slide plunger spring (722) in position with a finger, withdraw the drift punch UT 2012. • Gently release and then remove the cocking slide plunger spring (722) together with the cocking slide plunger (721) out of their housing in the cocking slide bracket (711) (right part of Fig. 9.8.k). To reassemble, follow the above steps in reverse order, taking into account the following points : - The cocking slide plunger spring (722) should be fitted into the (hollow) cocking slide plunger (721) and this assembly should then be inserted, with the tip of the plunger first, into the housing on top of the cocking slide bracket (711). - The pin (723) should not protrude after it has been reinstalled. Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

633 600 a

633 643

610

641 643

614

631

612 h b a

660

639 632

668 666 667

b

637 i

638 642

634

d c

23 x 635 614

614

g

h e

636

647 i

613

620

631 f

633

c

649 646 e

644

d

633 648

f

g

632

615

Fig. 9.9.a - Back plate group [ 9 ]

Although the upper handle arm (612), the lower handle arm (613) and the rivets (614) are available as spare parts, it is not recommended to intervene on them. If such interventions are nevertheless required, they may only be carried out by qualified technicians using the instructions and the tools which are only available on special request.

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.9.

BACK PLATE GROUP [ 9 ] (Fig. 9.9.a)

9.9.1.

Removal and reinstallation of a handle grip (632) and its tube (631) Requirements : • OREA 554 (Wrench, back plate handle screw) • UT 2030 (Center punch, dia. 6 mm) • UT 2111 (Hammer 250 g) • If necessary, remove the back plate group [ 9 ] as described for ‘field stripping’ in § 7.1. Please note that, for this operation, it is not absolutely necessary to remove the back plate group [ 9 ].

• Using the wrench OREA 554, take out one of the 2 screws (633) which secure the handle grip tube (631) (and therefore also the handle grip (632) itself) to the upper / lower handle arm (612) / (613) (left part of Fig. 9.9.b). Take into account that the heads of the screws (633) have been staked.

• Release and remove the handle grip (632) and its tube (631) from between the upper and lower handle arms (612) and (613) (right part of Fig. 9.9.b). • Using the wrench OREA 554, separate the remaining screw (633) from the handle grip tube (631). To reassemble, follow the above steps in reverse order, taking into account the following points : - Fit the handle grip (632) between the upper and lower handle arms (612) and (613) and then, from the upper / lower side, insert the handle grip tube (631) through the corresponding hole in the upper / lower handle. - After their reinstallation, secure the screws (633) by staking their head into the notch ‘a’ of the upper and lower handle arms (612) and (613) by using the center punch UT 2030 and the hammer UT 2111.

633

OREA 554

a

612

632 633

.

612 631

632

613

.

633

Fig. 9.9.b - Removal of a handle grip (632) and its tube (631) Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun a

620 a

) . 610 b

620

Fig. 9.9.c - Removal of the buffer tube sleeve (620)

OREA 800 + OREA 806

UT 2301 638

. 610

637 636

Fig. 9.9.d - Removal of the buffer disks screw (636) as well as the plunger (637) and its spring (638)

610

634 ‘23’ x 635 636

. Fig. 9.9.e - Removal of the fiber buffer disks (635) and the buffer plate (634) Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.9.

BACK PLATE GROUP [ 9 ] (continued)

9.9.2.

Removal and reinstallation of the buffer tube sleeve (620), the buffer plate (634), the fiber buffer disks (635) and the buffer disks screw (636) Requirements : • • • •

OREA 800 (Bush for OREA 801) OREA 806 (Tip and blade assembly, screwdriver) UT 1903 (Screwdriver 3 x 75 mm) UT 2301 (Torque wrench)

• Remove the back plate group [ 9 ] as described for ‘field stripping’ in § 7.1. Although, for reasons of clarity, the illustrations of the following procedure show the back plate group [ 9 ] without handle grips (632), it is not necessary to remove the handle grips.

NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the back plate group [ 9 ] can be fixed into a vice. When fixing the back plate group [ 9 ] into a vice, use special clamps or a rag to avoid scratches.

• Turn the buffer tube sleeve (620) clockwise when viewed from the rear side until its stud (a) comes out of the groove (b) in the buffer tube of the back plate subassembly (610) and then pull the sleeve rearwards off the buffer tube (Fig. 9.9.c). Please note that it is not absolutely necessary to remove the buffer tube sleeve (620) in order to enable the removal of the absorbing components provided inside the buffer tube of the back plate subassembly (610).

• At the rear side of the buffer tube of the back plate subassembly (610) and using the torque wrench UT 2301 (with bush OREA 800 and tip OREA 806), unscrew the buffer disks screw (636) until the plunger (637) becomes visible (Fig. 9.9.d). Please note that the plunger (637) is subjected to the pressure of its spring (638).

• While holding back the plunger (637) with a finger, continue unscrewing the buffer disks screw (636) until the plunger is released and then take the plunger, together with its spring (638), out of the screw (right part of Fig. 9.9.d). • Completely unscrew the buffer disks screw (636) and then take the fiber buffer disks (635) and the buffer plate (634) out of the rear side of the buffer tube of the back plate subassembly (610) (Fig. 9.9.e). To reassemble, follow the above steps in reverse order, taking into account the following points : - Insert the buffer plate (634) with its narrower end first. - When screwing the buffer disks screw (636) back into position, first screw until the housing for the plunger (637) and its spring (638) is just not covered by the rear edge of the buffer tube of the back plate subassembly (610). After that, fit the plunger (637) into the open extremity of its spring (638), fit this assembly into its housing in the buffer disks screw (636) and then, while pushing onto the plunger with the screwdriver UT 1903, continue screwing the buffer disks screw all the way in. - When tightening the buffer disks screw (636), apply a torque of 40.7 ± 13.5 Nm by using the torque wrench UT 2301 (with bush OREA 800 and tip OREA 806) and then check if the buffer disks screw protrudes by 0 - 3.3 mm from the buffer tube. If not, correct by changing the number of fiber buffer disks (normally ‘23’). If the buffer disks screw (636) is completely inside the buffer tube, add a fiber buffer disk. If the buffer disks screw protrudes by more than 3.3 mm, remove a disk.

- When reinstalling the buffer tube sleeve (620), ensure that its stud (a) fits correctly into the groove (b) in the buffer tube of the back plate subassembly (610). Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

UT 1803

644

647

644

.

. 615 646

613

613 615 644

644

646

647 Fig. 9.9.f - Removal of the back plate latch lock (644) and its spring (646)

a 613

613

649 UT 2003 642

648

642

648

.

Fig. 9.9.g - Removal of the back plate latch (648) and its spring (649)

Maintenance manual

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Catalog n° 3660084070

FN HERSTAL

MI.50 M2HB QCB machine gun

9.9.

BACK PLATE GROUP [ 9 ] (continued)

9.9.3.

Removal and reinstallation of the back plate latch lock (644) and its spring (646) Requirements : • UT 1803 (Half-round nose pliers) • If necessary, remove the back plate group [ 9 ] as described for ‘field stripping’ in § 7.1. Please note that, for this operation, it is not absolutely necessary to remove the back plate group [ 9 ]. Although, for reasons of clarity, the illustrations of the following procedure show the back plate group [ 9 ] without handle grips (632), it is not necessary to remove the handle grips.

• At the lower handle arm (613) and using the pliers UT 1803, pull the locking pin (615) out of the pin (647) (upper left part of Fig. 9.9.f). • Using the pliers UT 1803, withdraw the pin (647) and then remove the back plate latch lock (644) from the lower handle arm (613) (Fig. 9.9.f). • Using the pliers UT 1803, take the back plate latch lock spring (646) out of the back plate latch lock (644) (Fig. 9.9.f). To reassemble, follow the above steps in reverse order, taking into account that the 2 extremities of the back plate latch lock spring (646) should fit correctly into the corresponding holes in the back plate latch lock (644) and that the free end of the spring should be facing outwards (lower right part of Fig. 9.9.f).

9.9.4.

Removal and reinstallation of the back plate latch (648) and its spring (649) Requirements : • • • •

UT 1803 (Half-round nose pliers) UT 2003 (Drift punch, dia. 3.9 mm, lg 50 mm) UT 2004 (Drift punch, dia. 5 mm, lg 40 mm) UT 2111 (Hammer 250 g)

• Remove the back plate latch lock (644) as described in § 9.9.3. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the back plate group [ 9 ] can be fixed into a vice. When fixing the back plate group [ 9 ] into a vice, use special clamps or a rag to avoid scratches.

• Using the drift punch UT 2003 and the hammer UT 2111, drive out the (lower) pin (642) which secures the back plate latch (648) (left part of Fig. 9.9.g). Take into account that the extremities of the pin (642) have been staked.

• While holding the back plate latch (648) in position with a finger, withdraw the drift punch UT 2003. • Gently release and then remove the back plate latch (648) together with its spring (649) (right part of Fig. 9.9.g). To reassemble, follow the above steps in reverse order, taking into account the following points : - One of the extremities of the back plate latch spring (649) should correctly engage its housing in the back plate latch (648) while the other extremity of the spring should correctly engage the recess (a) provided underneath the lower handle arm (613). - The pin (642) should not protrude and its extremities should be staked by using the drift punch UT 2004 and the hammer UT 2111. Maintenance manual

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668

668

UT 1913 666

660 UT 1621

610 667 666 Fig. 9.9.h - Removal and disassembly of the safety assembly (660)

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9.9.

BACK PLATE GROUP [ 9 ] (continued)

9.9.5.

Removal/disassembly and reassembly/reinstallation of the safety assembly (660) Requirements : • • • •

UT 1110 (Open-end wrench 7 x 9 mm) UT 1621 (Hexagonal key 1/8”) UT 1913 (Screwdriver 5.5 x 150 mm) LOCTITE SCREWLOCK 222

• If necessary, remove the back plate group [ 9 ] as described for ‘field stripping’ in § 7.1. Please note that, for this operation, it is not absolutely necessary to remove the back plate group [ 9 ]. Although, for reasons of clarity, the left part of Fig. 9.9.h shows the back plate group [ 9 ] without handle grips (632), it is not necessary to remove the handle grips. Also for reasons of clarity, the left part of Fig. 9.9.h shows the back plate group [ 9 ] without bolt latch release (639) and trigger (641) (which are removed in the following § 9.9.6) : it is assumed that they are still mounted on the back plate group !

NOTE : If it has been removed, and in order to facilitate the following disassembling (and reassembling) procedure, the back plate group [ 9 ] can be fixed into a vice. When fixing the back plate group [ 9 ] into a vice, use special clamps or a rag to avoid scratches.

• Using the hexagonal key UT 1621, take out the 2 screws (668) in order to remove the safety assembly (660) from the rear side of the back plate subassembly (610) (left part of Fig. 9.9.h). Take into account that the threads of the screws (668) have been secured with glue.

• Using the screwdriver UT 1913, unscrew the screw (666) (together with the hexagonal nut (667)) from the safety catch of the safety assembly (660) (Fig. 9.9.h). • If necessary, unscrew the hexagonal nut (667) from the screw (666). To reassemble, follow the above steps in reverse order, taking into account the following points : - At their reinstallation, secure the screws (668) by applying glue such as ‘LOCTITE SCREWLOCK 222’ to their threads. - The screw (666) should be reinstalled so that it correctly holds back the trigger (641) when the safety catch is turned inwards under the trigger. - Once the screw (666) is installed correctly, use the wrench UT 1110 to screw the hexagonal nut (667) against the safety catch body. During this operation, which ensures that the screw (666) is secured into position, take care not to turn the screw inadvertently (hold the screw in position with the screwdriver UT 1913).

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UT 2003 642

. 641 612

643

639

610

641

a

642

639

Fig. 9.9.i - Removal of the bolt latch release (639), the trigger (641) and the springs (643)

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9.9.

BACK PLATE GROUP [ 9 ] (continued)

9.9.6.

Removal and reinstallation of the bolt latch release (639), the trigger (641) and the springs (643) Requirements : • • • • •

UT 2003 (Drift punch, dia. 3.9 mm, lg 50 mm) UT 2004 (Drift punch, dia. 5 mm, lg 40 mm) UT 2111 (Hammer 250 g) If necessary, UT 1110 (Open-end wrench 7 x 9 mm) If necessary, UT 1913 (Screwdriver 5.5 x 150 mm)

• Remove the back plate group [ 9 ] as described for ‘field stripping’ in § 7.1. • Turn the safety catch of the safety assembly (660) outwards. NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the back plate group [ 9 ] can be fixed into a vice. When fixing the back plate group [ 9 ] into a vice, use special clamps or a rag to avoid scratches.

• Using the drift punch UT 2003 and the hammer UT 2111, drive out the (upper) pin (642) which secures the bolt latch release (639) and the trigger (641) (upper part of Fig. 9.9.i). Take into account that the extremities of the pin (642) have been staked.

• While holding the bolt latch release (639) and the trigger (641) in position with a finger, withdraw the drift punch UT 2003. • Gently release and then remove the bolt latch release (639) and the trigger (641) together with the springs (643) (Fig. 9.9.i). To reassemble, follow the above steps in reverse order, taking into account the following points : - One of the extremities of the springs (643) should correctly engage its housing in the bolt latch release (639) / the trigger (641) while the other extremity of the springs should correctly engage the corresponding recess provided in the back plate subassembly (610) (lower right part of Fig. 9.9.i). - Reinstall first the bolt latch release (639) and then the trigger (641). Fit the bolt latch release (639) into the upper opening (a) in the back plate subassembly (610) so that its left side is against the left side of the opening. Fit the trigger (641) in position between the bolt latch release (639) and the right side of the opening (a).

- Ensure that the handle of the bolt latch release (639) is correctly positioned between the 2 forks of the trigger (641). - If it is difficult to insert the pin (642), use the drift punch UT 2003 to assist to align the holes in the bolt latch release (639) and the trigger (641) with the corresponding holes in the back plate subassembly (610). - The pin (642) should not protrude and its extremities should be staked by using the drift punch UT 2004 and the hammer UT 2111. - After the reinstallation, check and, if necessary, adjust the safety assembly (660) as described at the end of § 9.9.5. Maintenance manual

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2.75 cm

2 cm

-2 cm

-9 cm Line of sights

Target at 200 m

150 m

100 m

50 m

MI.50 M2HB QCB

Fig. 10.1.a - Trajectory of a bullet for a correct firing precision at a distance of 200 m (*)

MPI x x

x x x x

x

P

x x x

Target at 200 m

MPI

MPI P1

x

x x x x x

x

2.75 cm

x x

2 cm

x

x

P1

x x xx x x x x

x

-2 cm

xxxxx x x x xx

MPI P Target at 150 m

Target at 100 m

P

P1

P Target at 50 m

Fig. 10.1.b - Shooting at a target to check the firing precision (*)

(*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, refer to § 13.1.8.

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CHAPTER 10 : INSPECTION AND ADJUSTMENTS Before any intervention on the MI.50 M2HB QCB machine gun, ensure to be familiar with the safety information given in chapter 4 of this maintenance manual. Before any inspection or adjustment, ensure that the machine gun is perfectly clean.

10.1. CHECKING THE FIRING PRECISION (*) (Fig. 10.1.a and Fig. 10.1.b) NOTE : In order to increase the accuracy of the following checking procedure, it is recommended to use the machine gun on a tripod or to fix it in a fixing support such as a shooting adjustment device, ... In any case, eliminate the less accurate impact.

The firing precision should periodically be checked by proceeding as follows : • Turn the safety catch outwards so that the trigger (641) is no longer blocked into position and ensure that the bolt latch release (639) is unlocked and raised. • Set the machine gun for a shooting range of ‘200 m’. As a rule, the firing precision of the MI.50 M2HB QCB machine gun should be checked on a target located at 200 m. This checking procedure (and the following adjustment procedure) can also be carried out on a target located at less than 200 m as long as the necessary corrections are made to compensate for the trajectory of the bullet (Fig. 10.1.a). This checking procedure (and the following adjustment procedure) will therefore explain the corrections to be made for targets located at 50 m, 100 m and 150 m.

• Aim the machine gun at a well-determined point (P) on a safe target. Always aim at the point (P), independently of the distance of the target (Fig. 10.1.a and Fig. 10.1.b).

• Fire 10 single shots and eliminate the less accurate impact. • At the target, check if the 10-1 impacts are situated within a square with a side of 120 cm. In case of a target located at 50 / 100 / 150 m, the impacts should be situated within a square with a side of 30 / 60 / 90 cm.

If so, directly proceed to the next step. If not, repeat the shooting procedure at least twice. If, during these next tries, the 10-1 impacts are still not situated within a square with the appropriate side, this indicates that the barrel (110) / (110/1) of the machine gun is showing signs of wear : replace the barrel and then restart this checking procedure.

• At the target, determine the mean point of impact (MPI). • If the MPI corresponds to the point of aim (P) (target at 200 m) or to an imaginary point (P1) (2 cm under / 2 cm above / 2.75 cm above the point of aim (P) (target at 50 / 100 / 150 m)), the firing precision is correct. If not, the firing precision should be adjusted as described in the following § 10.2. Maintenance manual

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OREA 255

3826

3824

3854

Fig. 10.2.a - Turning the front sight (3824) in order to correct the vertical position of the MPI (*)

UT 1903 510 m

541

548

548

Fig. 10.2.b - Turning the rear sight windage knob (541) in order to correct the lateral position of the MPI (*)

547

Fig. 10.2.c - Correcting the position of the rear sight windage scale (547) (*)

(*) In case of a machine gun equipped with the ‘anti-aircraft sights’-kit, refer to § 13.1.8.

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10.2. ADJUSTMENT OF THE SIGHTS (*) Requirements : • OREA 255 (Wrench, front sight) • UT 1903 (Screwdriver 3 x 75 mm) The front sight (3824) and the rear sight assembly (500) should be adjusted after each intervention (removal, disassembling, ...) on the sights of the machine gun. They should also be adjusted if required by the checking procedure of the previous § 10.1. Proceed as follows : • Check the firing precision of the machine gun as described in § 10.1. If the MPI corresponds to the point of aim (P) (for targets located at 200 m) or to the imaginary point (P1) (for targets located at 50 / 100 / 150 m), the following adjustment procedure should not be carried out. If not, carry out the following adjustment procedure.

• If a vertical correction of the MPI is required, proceed as follows : Using the OREA 255 through the upper hole in the front sight cover (3826), turn the front sight (3824) in order to correct the vertical position of the MPI (Fig. 10.2.a). In order to raise the MPI, turn the front sight in the clockwise direction (downwards). In order to lower the MPI, turn the front sight in the counterclockwise direction (upwards). Take into account that each 90° turn of the front sight will change the vertical position of the MPI by 10 / 7.5 / 5 / 2.5 cm on a target located at 200 / 150 / 100 / 50 m.

• If a lateral correction of the MPI is required, proceed as follows : - Turn the rear sight windage knob (541) in order to correct the lateral position of the MPI (Fig. 10.2.b). In order to move the MPI towards the right (left) side, turn the rear sight windage knob (541) in the (counter)clockwise direction when viewed from the left side. Take into account that each 90° turn of the rear sight windage knob (541) will generate a click and that each click corresponds to a change of the lateral position of the MPI by 2.5 mils.

- After this lateral correction of the MPI, it is most probable that the ‘0’ line on the rear sight windage scale (547) is not correctly aligned with the mark ‘m’ on the rear sight leaf assembly (520) (Fig. 10.2.c). In such a case, correct the position of the rear sight windage scale (547) by proceeding as follows (Fig. 10.2.c) : - Using the screwdriver UT 1903, slightly loosen the 2 screws (548) which secure the rear sight windage scale (547) to the rear sight base (510). - Correct the position of the rear sight windage scale (547) and then tighten the 2 screws (548). • Check if the firing precision of the machine gun is now correct. If so, the adjustment is terminated. If not, repeat the adjustment procedure until a correct firing precision is obtained.

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10.3. CHECKING AND GAUGING THE BARREL (110) / (110/1) Preparation • Remove the barrel group [ 1 ] as described for ‘field stripping’ in § 7.1. • Thoroughly clean and dry the barrel (110) / (110/1) (refer to chapter 8). • Carry out a visual inspection of the outside of the barrel (110) / (110/1). • Carry out a visual inspection of the bore and the chamber of the barrel (110) / (110/1).

Checking the barrel (110) / (110/1) for keyholing (resulting in elongated impacts on a target) This checking procedure should only be carried out after the barrel (110) / (110/1) has been used intensively and/or in case of doubt about its condition.

• Correctly mount the barrel group [ 1 ] and load the machine gun. • Turn the safety catch outwards so that the trigger (641) is no longer blocked into position and ensure that the bolt latch release (639) is unlocked and raised. • Aim the machine gun at a safe target located at 25 m and fire 10 single shots. • At the target, check if the impacts are not too elongated (‘keyholed’ of 15° or more). An impact is keyholed of 15° when its length reaches 22 mm. If 20% or more of the impacts are keyholed of 15° or more, the bore of the barrel (110) / (110/1) shows serious signs of wear : the barrel should be rejected ! Otherwise, the barrel is OK.

• Repeat the ‘preparation’ procedure described above and then check the barrel (110) / (110/1) for coppering as described in the following paragraph.

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10.3. CHECKING AND GAUGING THE BARREL (110) / (110/1) (continued) Checking the barrel (110) / (110/1) for coppering This checking procedure should be carried out to check the bore of the barrel (110) / (110/1) for excessive copper deposit.

Requirements : • • • • • •

G093 (Copper gauge for STL and CHR .50 barrels) Distilled water H2O Ammonium persulphate Ammonium carbonate Ammonia Rubber plug for sealing the barrel at the side of the chamber

• Insert the copper gauge G093 into the chamber of the barrel (110) / (110/1) and ensure that it is able to enter the bore of the barrel at least until the reference line. • If so, the bore is not subjected to excessive coppering. If not, the copper fouling inside the bore of the barrel (110) / (110/1) should be removed by carrying out the following chemical procedure : - Prepare the following solution :

Distilled water H2O Ammonium persulphate Ammonium carbonate Ammonia

: : : :

336 cm3 84 g 42 g 528 cm3

- Ensure that the bore of the barrel (110) / (110/1) is perfectly clean and dry. - At the side of the chamber, seal the barrel (110) / (110/1) by using a rubber plug. - Fix the barrel (110) / (110/1) vertically into a vice, with its muzzle pointing upwards. When fixing the barrel (110) / (110/1) into a vice, use special clamps or a rag to avoid scratches.

- Completely fill the barrel (110) / (110/1) with the solution prepared above. - Wait 20-30 minutes, remove the barrel (110) / (110/1) from the vice and then pour the solution from the barrel into a flask or a clear glass : the solution will be tinted blue due to the presence of copper salt. - Repeat the 3 previous steps until the solution coming out of the barrel (110) / (110/1) is no longer tinted blue but keeps its original colour. When the solution keeps its original colour, the bore of the barrel (110) / (110/1) is considered being free from copper deposits.

- Remove the sealing and then thoroughly clean and dry the barrel (110) / (110/1) in order to remove any trace of the solution (refer to chapter 8). • Gauge the bore of the barrel (110) / (110/1) as described in the following paragraphs. NOTE : After having removed the coppering, it is absolutely necessary to gauge the bore of the barrel (110) / (110/1). Maintenance manual

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a

b

Fig. 10.3.a - Bullet lead inspection gauge (1650)

c 1650 110

Fig. 10.3.b - Gauging the bore of the chrome-plated barrel (110)

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10.3. CHECKING AND GAUGING THE BARREL (110) / (110/1) (continued) Gauging the bore of the chrome-plated barrel (110) Requirements : • 1650 (Bullet lead inspection) The following gauging procedure only applies to the bore of the chrome-plated barrel (110). The procedure requires the bullet lead inspection gauge (1650) which consists of a gauge rod (a) fitted into a gauge head (b) (Fig. 10.3.a). Never gauge a heated barrel (110) : it would result in incorrect gauging results and it can cause damage to the bullet lead inspection gauge (1650).

Proceed as follows (Fig. 10.3.b) : • From the side of the chamber, insert the bullet lead inspection gauge (1650), with the conical end of its gauge rod (a) first, into the bore of the barrel (110). • Position the gauge head (b) of the bullet lead inspection gauge (1650) so that its wider flat face (c) comes perfectly into contact with the rear end of the barrel (110). • Without applying excessive force, push the gauge rod (a) as far as possible into the barrel (110). • Check if the ‘80 mm’ graduation on the gauge rod (a) is still visible. Note that the ‘80 mm’ graduation corresponds to the second small red-painted groove on the gauge rod (a).

• If the ‘80 mm’ graduation is still visible, the condition of the barrel (110) is correct. If the ‘80 mm’ graduation has disappeared under the rear edge of the gauge head (b), the barrel (110) is worn and should be rejected. Please note that, if the ‘50 mm’ graduation has disappeared under the rear edge of the gauge head (b), the barrel (110) shows signs of wear and is therefore in a ‘warning’ condition.

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A

a

1690

b Fig. 10.3.c - Barrel gauges box (1695)

A 1690

c

a

b Fig. 10.3.d - Checking the barrel erosion gauge (A)

110/1

d

a

d

b

a

b 110/1

Gauging the (rear) stellited portion of the barrel (110/1)

Gauging the (front) chrome-plated portion of the barrel (110/1)

Fig. 10.3.e - Gauging the bore of the stellited barrel (110/1)

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10.3. CHECKING AND GAUGING THE BARREL (110) / (110/1) (continued) Gauging the bore of the stellited barrel (110/1) Requirements : • 1695 (Box, barrel gauges) The following gauging procedure only applies to the bore of the stellited barrel (110/1). The procedure requires the barrel gauges box (1695) which contains the barrel erosion gauge (A) and the calibrating gauge (1690) (Fig. 10.3.c). The barrel erosion gauge (A) consists of a gauge rod (a) fitted into a gauge tube (b).

(a) Checking the barrel erosion gauge (A) Before using the barrel erosion gauge (A), check it by proceeding as follows : - While holding the expanding part (c) of the barrel erosion gauge (A) into the hole of the calibrating gauge (1690), push the gauge rod (a) into the gauge tube (b) until the expanding part is expanded so that it comes fully into contact with the inner side of the hole of the calibrating gauge and that it exerts a light pressure on it (Fig. 10.3.d). - Check if the ‘reject’-mark on the gauge rod (a) is at the rear end of the gauge tube (b). If not, the barrel erosion gauge (A) is not OK.

(b) Gauging (Fig. 10.3.e) Never gauge a heated barrel (110/1) : it would result in incorrect gauging results and it can cause damage to the barrel erosion gauge (A).

- Set the gauge tube (b) for checking the (rear) stellited portion of the barrel (110/1) by positioning the stop (d) of the tube onto the front ‘H.B.’-mark (left part of Fig. 10.3.e). - From the side of the chamber, insert the gauge tube (b), with its expanding part (c) (also refer to Fig. 10.3.d) first, into the bore of the barrel (110/1) until the stop (d) touches the rear end of the barrel (left part of Fig. 10.3.e). - Without applying excessive force, push the gauge rod (a) as far as possible into the gauge tube (b). - The condition of the stellited portion of the barrel (110/1) is now determined by the visibility of the ‘reject’-mark and the mark just in front of it. If both marks are visible, the condition of the stellited portion of the barrel (110/1) is correct. If only the ‘reject’-mark is visible, the stellited portion of the barrel (110/1) shows signs of wear so that the barrel should be replaced as soon as possible. If both marks have disappeared under the rear edge of the gauge tube (b), the stellited portion of the barrel (110/1) is worn and the barrel should be rejected.

- Repeat the above procedure for the (front) chrome-plated portion of the barrel (110/1) after having positioned the stop (d) of the gauge tube (b) onto the rear ‘H.B.’-mark (right part of Fig. 10.3.e).

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1610

G097 1700

Fig. 10.4.a - Headspace adjustment device (1700) and headspace gauges (1610) and G097

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10.4. CHECKING AND GAUGING THE HEADSPACE With a cartridge present in the chamber of the barrel (110) / (110/1), the headspace is the distance between the bottom of the T-slot for the cartridges on the front face of the bolt (820) and a particular point on the front part of the cartridge case. This distance is very important as it determines if the weapon functions correctly and in all safety. A too large headspace can result in : - Insufficient support of the cartridge at the instant of firing. - Injury to the shooter. - Damage to the locking surfaces of the bolt (820) and the breech lock (221) as they are not perfectly into contact with each other at the instant of firing. A too small headspace, which can only result from a bad adjustment at the GM level (see further), can cause : - A failure to lock the moving parts.

As the headspace cannot be checked directly, it will be checked indirectly by using the headspace adjustment device (1700) in combination with an appropriate headspace gauge (Fig. 10.4.a). As explained in the following subparagraphs, the used headspace gauge depends on the maintenance level : FM/AM level GM level

(§ 10.4.1) : (§ 10.4.2) :

Headspace gauge (1610) Headspace gauge G097

Besides the periodic inspections, the headspace should also be checked and gauged after each intervention (removal, replacement, disassembling, ...) on the moving parts. The moving parts of the MI.50 M2HB QCB machine gun are the barrel extension group [ 3 ], the bolt group [ 5 ] and the buffer group [ 7 ].

It is especially important to check and gauge the headspace when replacing the breech lock (221) (also refer to § 9.3.2).

After having checked and adjusted the headspace, it is absolutely necessary to carry out the adjustment of the timing described in § 10.5.

If, during the adjustment of the headspace, the breech lock (221) is replaced by another one with a different number, it will be necessary to change the last two digits of the number combination marked on the upper front part of the bolt (820). If the barrel extension assembly (200) is replaced by another (new) one, it will be necessary to mark the barrel extension body (C1) or to change the existing mark. If the bolt assembly (810) is replaced by another (new) one, it will be necessary to mark the bolt (820) or to change the existing mark. For more information about the marking of the barrel extension body (C1) and the bolt (820), refer respectively to § 9.3.3. and § 9.5.9.

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1700

. 110 110/1

820

Fig. 10.4.b - Inserting the headspace adjustment device (1700) into the chamber of the barrel (110) / (110/1)

1610

820

Fig. 10.4.c - Using the headspace gauge (1610)

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10.4. CHECKING AND GAUGING THE HEADSPACE (continued) 10.4.1. Checking and gauging the headspace at the FM/AM level The checking and gauging procedure for the headspace at the FM (Field Maintenance) / AM (Advanced Maintenance) level allows checking and, if necessary, correcting the headspace by just changing the breech lock (221), without further interventions on the machine gun. If the following procedure does not allow an appropriate correction, the headspace should be checked and gauged at the (higher) GM (General Maintenance) level (refer to § 10.4.2).

Requirements : • 1610 (Headspace gauge .50 QCB) • 1700 (Device for adjustment headspace) • If necessary, requirements of § 9.3.2 (a) Checking procedure • Ensure that § 4.2. “Safety checks” has been carried out so that the trigger (641) is blocked into position and the bolt latch release (639) is unlocked and raised. • Open the feed cover (D1) by turning its latch shaft (440). • Pull the cocking handle (730) completely rearwards and hold it in that position. Please note that, after this operation, the bolt (820) is held back at its rear position.

• Insert the headspace adjustment device (1700), with its rear groove oriented vertically, into the chamber of the barrel (110) / (110/1) (Fig. 10.4.b). Do not release the cocking handle (730) in order to avoid any risk of trapping the fingers by an unexpected return of the bolt (820) !

• Push the cocking handle (730) back forwards. • Pointing the machine gun in a safe direction, push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. If, for any reason, the bolt (820) does not reach its most forward position and taking care not to trap the fingers, pull it forwards by inserting a screwdriver or a similar tool into its upper groove and using the upper plate of the receiver (3100) as a support.

• Ensure that the rear end of the headspace adjustment device (1700) touches the bottom of the T-slot for the cartridges on the front face of the bolt (820) (lower right part of Fig. 10.4.b). If not, try to obtain correct contact by again pulling the cocking handle (730) completely rearwards, pushing it back forwards and then letting the bolt (820) return towards its front position by repeating the previous step. If there is still not correct contact, check if the problem is not caused by dirt. If the problem cannot be solved by cleaning, the gun should be examined by a qualified armourer.

• Check if the .200 (GO) and the .212 (NO GO) ends of the headspace gauge (1610) enter into the space between the bottom of the rear (vertical) groove of the headspace adjustment device (1700) and the front face of the bolt (820) (Fig. 10.4.c). Do not apply excessive force.

• Pull the cocking handle (730) completely rearwards and hold it in that position. • Take the headspace adjustment device (1700) out of the chamber of the barrel (110) / (110/1). • Push the cocking handle (730) back forwards. Maintenance manual

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10.4. CHECKING AND GAUGING THE HEADSPACE (continued) 10.4.1. Checking and gauging the headspace at the FM/AM level (continued) (a) Checking procedure (continued) • Pointing the machine gun in a safe direction, push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position and then push down on the trigger (641) to release the firing pin (861). Never close the feed cover (D1) with the bolt (820) held back at its rear position !

• Close the feed cover (D1) and ensure that it locks correctly into position. (b) After the checking procedure The headspace is correct when the 2 following conditions are fulfilled : - The .200 (GO) end of the headspace gauge (1610) enters into the space between the bottom of the rear (vertical) groove of the headspace adjustment device (1700) and the front face of the bolt (820). If the .200 (GO) end cannot enter, the machine gun has been adjusted incorrectly : the machine gun should be sent for an intervention at the (higher) GM (General Maintenance) level (refer to § 10.4.2).

- The .212 (NO GO) end of the headspace gauge (1610) does not enter into the space between the bottom of the rear (vertical) groove of the headspace adjustment device (1700) and the front face of the bolt (820). If the .212 (NO GO) end can enter, replace the presently installed breech lock (221) by a spare breech lock with a 4 units higher (marked) number (also refer to § 9.3.2) and then repeat the checking and gauging procedure. The highest available breech lock number is ‘28’ : if the breech lock (221) which should be replaced has a number of ‘25’ or higher, the machine gun should be sent for an intervention at the (higher) GM (General Maintenance) level (refer to § 10.4.2).

If the breech lock (221) has been replaced by another one with a different number, it will be necessary to change the last two digits of the number combination marked on the upper front part of the bolt (820). For more information about the marking of the bolt (820), refer to § 9.5.9.

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If, during the adjustment of the headspace, the breech lock (221) is replaced by another one with a different number, it will be necessary to change the last two digits of the number combination marked on the upper front part of the bolt (820). If the barrel extension assembly (200) is replaced by another (new) one, it will be necessary to mark the barrel extension body (C1) or to change the existing mark. If the bolt assembly (810) is replaced by another (new) one, it will be necessary to mark the bolt (820) or to change the existing mark. For more information about the marking of the barrel extension body (C1) and the bolt (820), refer respectively to § 9.3.3. and § 9.5.9.

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10.4. CHECKING AND GAUGING THE HEADSPACE (continued) 10.4.2. Checking and gauging the headspace at the GM level The checking and gauging procedure for the headspace at the GM (General Maintenance) level allows checking and, if necessary, correcting the headspace by changing the breech lock (221) or by carrying out other interventions on the machine gun. In order to enable a future adjustment at the FM/AM level, the following procedure is more rigorous than the one described in § 10.4.1 : at the GM level, it is not allowed to correct the headspace by installing a breech lock (221) with a number of ‘25’ or higher.

Requirements : • 1700 (Device for adjustment headspace) • G097 (Headspace selection gauge) • If necessary, requirements of § 9.3.2 (a) Checking procedure • Insert the headspace adjustment device (1700), with its rear groove oriented vertically, into the chamber of the barrel (110) / (110/1) and check if it has been inserted correctly as described in § 10.4.1.a. • Check if the .202 (GO) and the .204 (NO GO) ends of the headspace gauge G097 enter into the space between the bottom of the rear (vertical) groove of the headspace adjustment device (1700) and the front face of the bolt (820) (also refer to Fig. 10.4.c). Do not apply excessive force.

• Remove the headspace adjustment device (1700) from the chamber of the barrel (110) / (110/1) and close the feed cover (D1) as described in § 10.4.1.a. (b) After the checking procedure The headspace is correct when the 2 following conditions are fulfilled : - The .202 (GO) end of the headspace gauge G097 enters into the space between the bottom of the rear (vertical) groove of the headspace adjustment device (1700) and the front face of the bolt (820). If the .202 (GO) end cannot enter, replace the presently installed breech lock (221) by a spare breech lock with a 1 unit lower (marked) number and then repeat the checking and gauging procedure.

- The .204 (NO GO) end of the headspace gauge G097 does not enter into the space between the bottom of the rear (vertical) groove of the headspace adjustment device (1700) and the front face of the bolt (820). If the .204 (NO GO) end can enter, replace the presently installed breech lock (221) by a spare breech lock with a 1 unit higher (marked) number and then repeat the checking and gauging procedure. Although the highest available breech lock number is ‘28’ and in order to enable a future adjustment at the FM/AM level, it is not allowed to correct the headspace at the GM level by installing a breech lock (221) with a number of ‘25’ or higher.

If a breech lock (221) with a marked number less than ‘13’ or exceeding ‘24’ is required to correct the headspace, there is a major problem with the machine gun. In such a case, first replace the barrel extension assembly (200) and then check if the headspace can be gauged and corrected as described above. If the problem is not solved, check if it can be solved by replacing the bolt assembly (810). If the problem is still not solved, the complete moving parts should be replaced.

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Fig. 10.5.a - Timing gauge (1645)

1645

B1

200

Fig. 10.5.b - Using the ‘NO FIRE’ gauge plate of the timing gauge (1645) Maintenance manual

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10.5. TIMING ADJUSTMENT The timing adjustment ensures that the cartridge is not fired too early or too late. In case of too early firing, the machine gun would operate incorrectly (problems with the extraction of the cartridges from the ammunition belt, short recoil of the moving parts, ...). Too late firing could cause serious damage to the front part of the receiver (3100), the barrel extension group [ 3 ] and the front face of the bolt (820).

The timing will be checked by using the timing gauge (1645) which consists of the 3 following gauge plates (Fig. 10.5.a) : - a ‘NO FIRE’ gauge plate (2.95 mm / .116”) - a ‘FIRE’ gauge plate (1.50 mm / .059”) - a ‘REJECT’ gauge plate (0.51 mm / .020”) Besides the periodic inspections, the timing should also be checked after having checked and gauged the headspace and after each intervention (removal, replacement, disassembling, ...) on the moving parts, the trigger bar (3846) and the breech lock cam (3816). The moving parts of the MI.50 M2HB QCB machine gun are the barrel extension group [ 3 ], the bolt group [ 5 ] and the buffer group [ 7 ].

As the timing is adjusted by means of the trigger bar stop knurled nut (3651), it is especially important to check the timing after any intervention on this nut (also refer to § 9.2.13).

10.5.1. Checking the timing The following checking procedure allows checking at the FM (Field Maintenance) / AM (Advanced Maintenance) level if the timing lays between the limits of a safe use of the machine gun.

Requirements : • 1645 (Fixed timing gauge) • Ensure that § 4.2. “Safety checks” has been carried out. • Open the feed cover (D1) by turning its latch shaft (440). • Pull the cocking handle (730) completely rearwards and push it back forwards. Please note that, after this operation, the bolt (820) is held back at its rear position and the firing pin (861) is cocked.

• Pointing the machine gun in a safe direction, push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. If, for any reason, the bolt (820) does not reach its most forward position and taking care not to trap the fingers, pull it forwards by inserting a screwdriver or a similar tool into its upper groove and using the upper plate of the receiver (3100) as a support.

• Pull the cocking handle (730) rearwards, just enough to move the moving parts rearwards by approx. 5 mm, and hold it in that position. • Insert the ‘NO FIRE’ gauge plate of the timing gauge (1645) between the front face of the barrel extension assembly (200) and the inner part of the receiver frame (B1) (Fig. 10.5.b). • Release the cocking handle (730) so that the moving parts move back forwards and come into contact with the ‘NO FIRE’ gauge plate of the timing gauge (1645). • Unblock the trigger (641) and push down on it : the firing pin (861) must not operate. Maintenance manual

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1645

1645

B1 B1 200 200

Fig. 10.5.c - Using the ‘FIRE’ gauge plate of the timing gauge (1645)

Fig. 10.5.d - Using the ‘REJECT’ gauge plate of the timing gauge (1645)

B1 OREA 797

3653 B5

3651

Fig. 10.5.e - Temporarily fixing the trigger bar stop assembly (B5) by using the OREA 797

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10.5. TIMING ADJUSTMENT (continued) 10.5.1. Checking the timing (continued) • Pull the cocking handle (730) rearwards, just enough to move the moving parts rearwards by approx. 5 mm, and hold it in that position. • Replace the ‘NO FIRE’ gauge plate of the timing gauge (1645) by the ‘FIRE’ gauge plate (Fig. 10.5.c). • Release the cocking handle (730) so that the moving parts move back forwards and come into contact with the ‘FIRE’ gauge plate of the timing gauge (1645). • Push down on the trigger (641) : the firing pin (861) must operate. • Remove the ‘FIRE’ gauge plate of the timing gauge (1645), close the feed cover (D1) (ensure that it locks correctly into position) and then block the trigger (641). • If both above conditions are fulfilled, the timing is correct. If one or both of the above conditions are not fulfilled, the timing should be adjusted at the GM (General Maintenance) level as described in § 10.5.2 and then checked again as described above. NOTE : The firing pin (861) must always operate with the ‘REJECT’ gauge plate of the timing gauge (1645) (Fig. 10.5.d). If the firing pin (861) does not operate with the ‘REJECT’ gauge plate of the timing gauge (1645), the gun should be restricted for further use and examined by a qualified armourer.

10.5.2. Adjustment of the timing The following adjusting procedure, which is intended for the GM (General Maintenance) level, allows a precise adjustment of the timing if required by the checking procedure of § 10.5.1, after each intervention on the headspace or after replacement of the moving parts, the trigger bar (3846), the breech lock cam (3816) and especially the trigger bar stop knurled nut (3651).

Requirements : • 1645 (Fixed timing gauge) • OREA 797 (Adjusting screw) • If not already used, requirements of § 9.2.13 • Ensure that § 4.2. “Safety checks” has been carried out. • If not already done, remove the trigger bar stop assembly (B5) as described in § 9.2.13. • Temporarily reinstall the trigger bar stop assembly (B5) on the inner upper rear part of the receiver frame (B1) by using the OREA 797 instead of the (longer) screw (3654) (Fig. 10.5.e). Ensure that the upper face of the trigger bar stop bracket (3653) comes perfectly into contact with the receiver frame (B1).

• Screw or unscrew the trigger bar stop knurled nut (3651) until its lower face is flush with the lower end of the threaded pin of the trigger bar stop bracket (3653). • Unscrew the trigger bar stop knurled nut (3651) by 1 turn (approx. 1 mm) in the counterclockwise direction when viewed from underneath.

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1645

B1

200

Fig. 10.5.f - Using the ‘FIRE’ gauge plate of the timing gauge (1645)

B1

3654

B5

3651

Fig. 10.5.g - Final installation of the trigger bar stop assembly (B5) Maintenance manual

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10.5. TIMING ADJUSTMENT (continued) 10.5.2. Adjustment of the timing (continued) • While ensuring that the upper face of the trigger bar stop bracket (3653) is and remains perfectly into contact with the receiver frame (B1), reinstall the back plate assembly (600) as described for ‘field stripping’ in § 7.2. • Open the feed cover (D1) by turning its latch shaft (440). • Pull the cocking handle (730) completely rearwards and push it back forwards. Please note that, after this operation, the bolt (820) is held back at its rear position and the firing pin (861) is cocked.

• Pointing the machine gun in a safe direction, push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. If, for any reason, the bolt (820) does not reach its most forward position and taking care not to trap the fingers, pull it forwards by inserting a screwdriver or a similar tool into its upper groove and using the upper plate of the receiver (3100) as a support.

• Pull the cocking handle (730) rearwards, just enough to move the moving parts rearwards by approx. 5 mm, and hold it in that position. • Insert the ‘FIRE’ gauge plate of the timing gauge (1645) between the front face of the barrel extension assembly (200) and the inner part of the receiver frame (B1) (Fig. 10.5.f). • Release the cocking handle (730) so that the moving parts move back forwards and come into contact with the ‘FIRE’ gauge plate of the timing gauge (1645). • Unblock the trigger (641) and push down on it : check if the firing pin (861) operates. If the firing pin (861) does not operate, repeat the above procedure by each time screwing the trigger bar stop knurled nut (3651) by two notches in the clockwise direction when viewed from underneath until the firing pin operates and then unscrew the nut by two notches in the counterclockwise direction. If the firing pin (861) operates, repeat the above procedure by each time unscrewing the trigger bar stop knurled nut (3651) by two notches in the counterclockwise direction when viewed from underneath until the firing pin does not operate anymore. Between two checks, always remove and then reinsert the ‘FIRE’ gauge plate of the timing gauge (1645).

• After having carried out the instructions of the previous step, repeat the above procedure by each time screwing the trigger bar stop knurled nut (3651) by one notch in the clockwise direction when viewed from underneath until the firing pin operates. • Without turning the trigger bar stop knurled nut (3651), remove the trigger bar stop assembly (B5) from the inner upper rear part of the receiver frame (B1) by taking out the OREA 797 (also refer to Fig. 10.5.e). • Reinstall the trigger bar stop assembly (B5) on the inner upper rear part of the receiver frame (B1) by using the (longer) screw (3654) (Fig. 10.5.g). During this operation, the trigger bar stop knurled nut (3651) should not be turned more than to allow its blocage by the engagement of the (long) screw (3654) into one of its notches !

• Reinstall the back plate assembly (600) as described for ‘field stripping’ in § 7.2. • Check the timing as described in § 10.5.1. Maintenance manual

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NO GO

G028

MAX

1671 GO

MIN

820 820

861

a Fig. 10.6.a - Inspection of the T-slot (a) for the cartridges on the front face of the bolt (820)

Fig. 10.6.b - Inspection of the firing pin protrusion

820

b

1673 Fig. 10.6.c - Inspection of the firing pin hole (b) in the front face of the bolt (820)

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10.6. CHECKING THE BOLT GROUP [ 5 ] Before carrying out the following inspections, remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1 and then clean it thoroughly.

Inspection of the T-slot for the cartridges on the front face of the bolt (820) (Fig. 10.6.a) Requirements : • 1671 (Gauge, checking, length, cartridge slot) The T-slot (a) for the cartridges on the front face of the bolt (820) should periodically be checked by using the T-slot checking gauge (1671). Ensure that the GO end of the gauge can pass freely through the T-slot while the NO GO end (be very careful !) cannot pass through it. If one of these conditions is not fulfilled, the bolt (820) should be replaced.

Inspection of the firing pin protrusion (Fig. 10.6.b) Requirements : • G028 (Firing pin protrusion) • Screwdriver or similar tool The firing pin protrusion should periodically be checked by using the firing pin protrusion gauge G028. • Cock the firing pin (861) by pushing the cocking lever (865) forwards. • Pull the cocking lever (865) completely rearwards and then, with the tip of a screwdriver or a similar tool, push down on the sear (863) in order to release the firing pin (861). • At the front face of the bolt (820), ensure that the MAX notch of the firing pin protrusion gauge G028 can be placed over the protruding end of the firing pin (861). If this condition is not fulfilled, the firing pin (861) should be replaced.

Inspection of the firing pin hole in the front face of the bolt (820) (Fig. 10.6.c) Requirements : • 1673 (Gauge, checking, firing pin hole) The firing pin hole (b) in the front face of the bolt (820) should periodically be checked by using the firing pin hole checking gauge (1673). • Cock the firing pin (861) by pushing the cocking lever (865) forwards. • Ensure that it is not possible to insert the gauge into the firing pin hole. If it is possible to insert the gauge, the bolt (820) should be replaced.

After the inspections, reassemble the machine gun as described in § 7.2.

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CHAPTER 11 : TROUBLESHOOTING Before any intervention on the MI.50 M2HB QCB machine gun, ensure to be familiar with the safety information given in chapter 4 of this maintenance manual.

11.1. THE GUN DOES NOT FIRE CORRECTLY WHEN THE TRIGGER (641) IS PUSHED DOWN The following procedures will normally solve almost all the problems which are not caused by the breakage of parts. First try if the problem can be solved by procedure 1. If the problem is not solved, try procedure 2. If the 2 procedures do not solve the problem, check if none of the typical problems given in § 11.2 has occurred. If the problem is still not solved, the gun should be restricted for further use and examined by a qualified armourer.

Procedure 1 • Pull the cocking handle (730) completely rearwards and push it back forwards. - If the machine gun has been set for automatic firing, the bolt (820) will not be held back at its rear position : it will return towards its front position. - If the machine gun has been set for single-shot firing, the bolt (820) will be held back at its rear position : push down on the bolt latch release (639) in order to release the bolt so that the latter returns towards its front position. Ensure that, in either firing mode, this step causes the cartridge which should have been fired, to be ejected out of the machine gun. If the cartridge is not ejected, immediately proceed to procedure 2.

• Pointing it in a safe direction, try if the machine gun now fires correctly when the trigger (641) is pushed down. If not, try if the problem can be solved by carrying out procedure 2.

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11.1. THE GUN DOES NOT FIRE CORRECTLY WHEN THE TRIGGER (641) IS PUSHED DOWN (continued) Procedure 2 • Turn the safety catch inwards under the trigger (641) so that the latter is blocked into position. • Ensure that the bolt latch release (639) is unlocked and raised. If the bolt latch release (639) is locked in its lower position by the lock of the buffer tube sleeve (620), unlock it by turning the sleeve clockwise when viewed from the rear side.

• Open the feed cover (D1) by turning its latch shaft (440) and then release and remove the ammunition belt. To release the ammunition belt, it will be necessary to raise the extractor/ejector assembly (840) : do not forget to lower the assembly after having removed the ammunition belt. If present, remove any link from the feed tray of the receiver (3100).

• Pull the cocking handle (730) completely rearwards and push it back forwards. Please note that, after this operation, the bolt (820) is held back at its rear position.

• Push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. • Pull the cocking handle (730) again completely rearwards and push it back forwards. Please note that, after this operation, the bolt (820) is again held back at its rear position.

• Ensure that the front face of the bolt (820) is free from ammunition. If there is a cartridge on the front face of the bolt (820), try to remove it by pushing downwards on the rim of its case with a tool such as a screwdriver or pliers. During this operation, NEVER touch the primer of the cartridge with the tool (in order to avoid any risk of explosion) and ensure that the barrel is ALWAYS pointing in a safe direction !

• Ensure that the inside of the machine gun is not excessively soiled (sand, mud, ...). • Pointing the gun in a safe direction, push down on the bolt latch release (639) in order to release the bolt (820) so that the latter returns towards its front position. • Reload the machine gun. • Pointing it in a safe direction, try if the machine gun now fires correctly when the trigger (641) is pushed down.

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11.2. TYPICAL PROBLEMS Problem Problem with the ammunition belt

Cause

Solution

---> • Incorrectly positioned ammunition belt

---> Correct the position of the ammunition belt

• Incorrectly assembled ammunition belt

---> Use a correctly assembled ammunition belt

• Damaged cartridge(s) and/ or link(s)

---> Remove the corresponding cartridge(s) and link(s) from the ammunition belt

Problem when extracting the ---> Broken, worn or deformed cartridge from the ammunition extractor/ejector assembly belt (840)

---> Replace the extractor/ejector assembly (840)

The cartridge does not enter the chamber

---> Clean the chamber

---> • Soiling, oxidation or scratches in the chamber

If necessary, replace the barrel (110) / (110/1) • Damaged (previous) cartridge

---> Remove the cartridge If necessary, use the ruptured case extractor (1073) as described in § 11.3

Failure to lock

---> Too small headspace

---> Check and gauge the headspace as described in § 10.4

Failure to fire

---> • Wrong timing

---> Adjust the timing as described in § 10.5

Short recoil

• Defective cartridge

---> Remove the cartridge

• Broken, worn or deformed firing pin (861)

---> Replace the firing pin (861)

• Incorrect operation of the firing pin (861)

---> Check the operation of the firing pin (861)

---> Defective or damaged cartridge

---> Remove the cartridge If necessary, use the ruptured case extractor (1073) as described in § 11.3

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11.2. TYPICAL PROBLEMS (continued) Problem

Cause

Failure to extract the cartridge from the chamber

Solution

---> • Soiling, oxidation or scratches in the chamber

---> Clean the chamber If necessary, replace the barrel (110) / (110/1)

• Damaged cartridge

---> Remove the cartridge If necessary, use the ruptured case extractor (1073) as described in § 11.3

• Too large headspace

Failure to eject the cartridge

---> • Defective cartridge

• Defective ejector (842)

---> Check and gauge the headspace as described in § 10.4 ---> Unload and reload the machine gun ---> Replace the ejector (842)

11.3. REMOVAL OF A RUPTURED CARTRIDGE CASE Too large headspace, defective ammunition, excessive soiling or wear of the chamber, ... can cause the rupture of a cartridge case, often resulting in an explosion of the cartridge at the instant of firing.

Requirements : • 1073 (Ruptured case extractor) If a ruptured cartridge case cannot be removed from the chamber as described in § 6.4 or § 11.1, use the ruptured case extractor (1073) by proceeding as follows : • While holding the moving parts rearwards by using the cocking handle (730), fit the ruptured case extractor (1073) with its rear end into the T-slot for the cartridges on the front face of the bolt (820). • Push down on the bolt latch release (639) in order to release the bolt (820). • Move the cocking handle (730) back forwards so that the bolt (820) pushes the ruptured case extractor (1073) into the chamber. During this operation, ensure that the ruptured case extractor (1073) is and remains correctly aligned with the chamber.

• While pulling the cocking handle (730) again rearwards, ensure that the remaining parts of the cartridge are extracted from the chamber. If it is still impossible to remove the (ruptured) cartridge case, the barrel group [ 1 ] should be restricted for further use (replace it by another one) and examined by a qualified armourer.

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831 a

820 b 823

c

831 Fig. 12.1.a - Changing the orientation of the bolt switch (831)

831

820 840 Fig. 12.1.b - Reinstallation of the extractor/ejector assembly (840)

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CHAPTER 12 : SPECIAL INTERVENTIONS Before any intervention on the MI.50 M2HB QCB machine gun, ensure to be familiar with the safety information given in chapter 4 of this maintenance manual.

12.1. CHANGING THE MACHINE GUN FROM LEFT-HAND TO RIGHTHAND FEEDING NOTE : Changing the MI.50 M2HB QCB machine gun from left-hand to right-hand feeding requires 2 new components : the link stripper (3829) and the rear cartridge stop (3830). A link stripper (3829) and a rear cartridge stop (3830) are supplied, together with a cocking handle spring (716/2), in the optional accessory kit (8997/2) (refer to § 14.2). Please note that the cocking handle spring (716/2) will not be used during the following procedure : it will be used when, if desired, the cocking handle assembly (H1) is moved towards the left side of the machine gun (also refer to § 12.2). Also note that, when changing the machine gun from left-hand to right-hand feeding, it is not necessary to move the cocking handle assembly (H1) towards the left side of the machine gun.

12.1.1. Interventions on the bolt group [ 5 ] • Remove the bolt assembly (810) as described for ‘field stripping’ in § 7.1. • Remove the extractor/ejector assembly (840) as described in § 9.5.1. • Lift the bolt switch (831) high enough to disengage its hole (a) from the pin (823) (upper left part of Fig. 12.1.a). • Turn the bolt switch (831) by approx. 180° in order to align its opposite hole (b) with the pin (823) and then lower the bolt switch back into position (lower right part of Fig. 12.1.a). As a result, the groove (c) of the bolt switch (831) will now face the inscription ‘R’ on the upper side of the bolt (820).

• While holding the extractor/ejector assembly (840) in the vertical position, reinstall it into its housing in the left side of the bolt (820). Take into account that the hinge pin of the extractor/ejector assembly (840) is also used to hold the bolt switch (831) into position.

• Rotate the extractor/ejector assembly (840) forwards to the horizontal position (Fig. 12.1.b). • Reinstall the bolt assembly (810) as described for ‘field stripping’ in § 7.2.

12.1.2. Interventions on the feed cover group [ 4 ] Requirements : • • • •

UT 1803 (Half-round nose pliers) UT 1903 (Screwdriver 3 x 75 mm) UT 2012 (Drift punch, dia. 3.5 mm, lg 27 mm) UT 2111 (Hammer 250 g)

• Open the feed cover (D1) by turning its latch shaft (440). Maintenance manual

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MI.50 M2HB QCB machine gun

430

430

477

477

.

460

450

450

478

460

Fig. 12.1.c - Reassembly of the belt feed slide assembly (D2) for a right-hand fed machine gun

473 475 471

c

477 b

D2

a

d

410

Fig. 12.1.d - Installation of the belt feed lever (471) and the belt feed slide assembly (D2) for a righthand fed machine gun

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MI.50 M2HB QCB machine gun

12.1. CHANGING THE MACHINE GUN FROM LEFT-HAND TO RIGHTHAND FEEDING (continued) 12.1.2. Interventions on the feed cover group [ 4 ] (continued) • Remove the belt feed lever (471) and the belt feed slide assembly (D2) as described in § 9.4.2. • Disassemble the belt feed slide assembly (D2) as described in § 9.4.3. • Reassemble the belt feed pawl (430) and its arm (477) for right-hand feeding (left part of Fig. 12.1.c). Please note that, for a right-hand fed machine gun, the belt feed pawl arm (477) should be fitted onto the opposite side of the belt feed pawl (430) as for a left-hand fed machine gun.

• Fit the assembly formed by the belt feed pawl (430) and its arm (477), together with the pawl spring (478), into the belt feed slide (450) (left part of Fig. 12.1.c). The wider extremity of the L-shaped pawl spring (478) should correctly engage its housing in the belt feed pawl (430) while the other extremity of the spring should correctly fit into the notch provided in the belt feed slide (450). On the other hand, the L-shaped pawl spring (478) should be oriented so that its body is at the side of the belt feed pawl arm (477).

• While pressing on the belt feed pawl (430), align the hole in the pawl and its arm with the holes of the belt feed slide (450) and then, from any side, reinstall the pin (460) by inserting it through the aligned holes (Fig. 12.1.c). The pin (460) should not protrude after it has been reinstalled.

• Reinstall the belt feed lever (471) and the belt feed slide assembly (D2) by proceeding as follows (Fig. 12.1.d) : - Fit the correctly oriented belt feed lever (471) onto the mounting pin (a) of the feed cover body (410). - Lightly lubricate the belt feed lever pin (475) and the spring (474). - Fit the belt feed lever pin (475) into the spring (474) and then insert this assembly, with the spring first, into the housing (b) in the belt feed lever (471) just before this housing is at the same height of the edge of the feed cover body (410) when sliding the belt feed lever back onto the mounting pin (a). Hold the belt feed lever pin (475) in place with the screwdriver UT 1903. Please note that, for a right-hand fed machine gun, the housing (b) in the belt feed lever (471) is used while the hole (c) is used for a left-hand fed machine gun.

- Just after the belt feed lever pin (475) has been held back, insert the belt feed slide assembly (D2) into its housing in the feed cover body (410) and then align its notch (d) with the front end of the belt feed lever (471). The belt feed slide assembly (D2) should be reinstalled so that the belt feed pawl arm (477) is at the rear side when the feed cover (D1) is closed.

- Push the belt feed lever (471) completely onto the mounting pin (a) and ensure that its front end correctly engages the notch (d) of the belt feed slide assembly (D2). - Using the pliers UT 1803, fit the retaining spring (473) into the hole in the mounting pin (a) in order to secure the belt feed lever (471). Maintenance manual

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MI.50 M2HB QCB machine gun

3834

3600

3835

3827 3834 Fig. 12.1.e - Installation of the belt holding pawls assembly (3600) for a right-hand fed machine gun

3828 3829

3835

3830

Fig. 12.1.f - Installation of the rear cartridge stop (3830), the link stripper (3829) and the front cartridge stop (3828) for a right-hand fed machine gun

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MI.50 M2HB QCB machine gun

12.1. CHANGING THE MACHINE GUN FROM LEFT-HAND TO RIGHTHAND FEEDING (continued) 12.1.3. Interventions on the feed tray Requirements : • UT 1803 (Half-round nose pliers) • If not already done, open the feed cover (D1) by turning its latch shaft (440). • At the right side of the machine gun, remove the rear cartridge stop assembly (3500) and the front cartridge stop (3828) as described in § 9.2.1. Contrary to the front cartridge stop (3828), the rear cartridge stop assembly (3500) will not be reinstalled during the following procedure : it will be replaced by the link stripper (3829) and the rear cartridge stop (3830) which are supplied in the optional accessory kit (8997/2).

• At the left side of the machine gun, remove the belt holding pawls assembly (3600) as described in § 9.2.3. • At the right side of the machine gun, install the belt holding pawls assembly (3600), together with the 2 pawl springs (3827), into its mounting support of the feed tray (left part of Fig. 12.1.e). One of the extremities of each pawl spring (3827) should correctly engage one of the holes of the mounting support while the other extremity of the spring should correctly enter into the hole in the bottom of the corresponding belt holding pawl.

• While pressing on the belt holding pawls assembly (3600), align its hole with the holes in the mounting support and then, from the rear side, push one of the mounting pins (3835) completely home (Fig. 12.1.e). • Using the pliers UT 1803, secure the mounting pin (3835) by inserting one of the locking pins (3834) into the hole at its front end (Fig. 12.1.e). • At the left side of the machine gun, fit the correctly oriented rear cartridge stop (3830) into its mounting slot of the feed tray (Fig. 12.1.f). The rear cartridge stop (3830) is supplied in the optional accessory kit (8997/2).

• Align the hole in the rear cartridge stop (3830) with the holes in the mounting slot of the feed tray and then, from the rear side, insert the remaining mounting pin (3835) into the aligned holes, just far enough to secure the stop into position (Fig. 12.1.f). • Fit the correctly oriented link stripper (3829) into its mounting slot of the feed tray, align its hole with the holes in the mounting slot and then push the mounting pin (3835) further forwards until the link stripper is correctly secured into position (Fig. 12.1.f). The link stripper (3829) is also supplied in the optional accessory kit (8997/2).

• Fit the correctly oriented front cartridge stop (3828) into its mounting slot of the feed tray, align its hole with the holes in the mounting slot and then push the mounting pin (3835) completely home (Fig. 12.1.f). • Using the pliers UT 1803, secure the mounting pin (3835) by inserting the remaining locking pin (3834) into the hole at its front end. • Close the feed cover (D1) and ensure that it locks correctly into position.

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UT 2111 UT 1180 730 UT 2030

713 730

713

Fig. 12.2.a - Reassembly of the cocking handle (730) and the cocking slide lever (713) for a left-hand mounted cocking handle assembly (H1)

.

.

UT 1910

726

726 711 Fig. 12.2.b - Changing the cocking slide stud (726) for a left-hand mounted cocking handle assembly (H1) Maintenance manual

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12.2. MOVING THE COCKING HANDLE ASSEMBLY (H1) FROM THE RIGHT SIDE TOWARDS THE LEFT SIDE OF THE MACHINE GUN NOTE : Moving the cocking handle assembly (H1) from the right side towards the left side of the machine gun requires 1 new component : the cocking handle spring (716/2). A cocking handle spring (716/2) is supplied, together with a link stripper (3829) and a rear cartridge stop (3830), in the optional accessory kit (8997/2) (refer to § 14.2). Please note that, when changing the machine gun from left-hand to right-hand feeding, it is not necessary to move the cocking handle assembly (H1) towards the left side of the machine gun.

Requirements : • • • • • • • •

UT 1180 (Open-end wrench 5/8 x 3/4”) UT 1802 (Cutting pliers) UT 1803 (Half-round nose pliers) UT 1808 (Lock wire pliers) UT 1910 (Screwdriver 10 x 200 mm) UT 1913 (Screwdriver 5.5 x 150 mm) UT 2030 (Center punch, dia. 6 mm) UT 2111 (Hammer 250 g)

• At the right side of the machine gun, remove the cocking handle assembly (H1) as described in § 9.8.1. • Taking into account that the cocking slide assembly (H2) will be released, remove the assembly formed by the cocking slide lever (713) and the cocking handle (730) as well as the cocking handle spring (716/1) as described in § 9.8.3. The cocking handle spring (716/1) will not be reinstalled during the following procedure : it will be replaced by the cocking handle spring (716/2) which is supplied in the optional accessory kit (8997/2).

• Unscrew the cocking handle (730) from the cocking slide lever (713) as described in § 9.8.3. • If the cocking slide lever (713) is fixed into a vice, take it out of the vice, turn it over and then fix it back into the vice. When fixing the cocking slide lever (713) into a vice, use special clamps or a rag to avoid scratches. Please note that, for a left-hand mounted cocking handle assembly (H1), the cocking handle (730) should be fitted onto the opposite side of the cocking slide lever (713) as for a right-hand mounted cocking handle assembly.

• Manually screw the cocking handle (730) into the cocking slide lever (713) (left part of Fig. 12.2.a). • Using the wrench UT 1180, fully tighten the cocking handle (730) into the cocking slide lever (713) (left part of Fig. 12.2.a). • Secure the cocking handle (730) to the cocking slide lever (713) by staking its threaded end by using the center punch UT 2030 and the hammer UT 2111 (right part of Fig. 12.2.a). • Take the assembly formed by the cocking slide lever (713) and the cocking handle (730) out of the vice. • Using the screwdriver UT 1910, unscrew the cocking slide stud (726) from the cocking slide bracket (711) (left part of Fig. 12.2.b). • Using the screwdriver UT 1910, screw and tighten the cocking slide stud (726) back into its opposite hole in the cocking slide bracket (711) (right part of Fig. 12.2.b). Maintenance manual

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MI.50 M2HB QCB machine gun 717

719

730

715

713 b

716/2 711

a

724 714

712

H2

Fig. 12.2.c - Reassembly of a cocking handle assembly (H1) for left-hand mounting

718 H1 B1

711

Fig. 12.2.d - Installation of the cocking handle assembly (H1) onto the left side of the machine gun

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12.2. MOVING THE COCKING HANDLE ASSEMBLY (H1) FROM THE RIGHT SIDE TOWARDS THE LEFT SIDE OF THE MACHINE GUN (continued) • While holding the cocking slide bracket (711) at its correct orientation for its installation onto the left side of the machine gun, fit the cocking slide assembly (H2), from the right side, into its slot in the cocking slide bracket (left part of Fig. 12.2.c). The cocking slide assembly (H2) should be oriented so that the cocking slide stop pin (724) is at the front side and is facing outwards. Ensure that the cocking slide plunger (721), which is now at the lower side of the cocking slide bracket (711), correctly engages the V-notch in the bottom of the cocking slide (712).

• From the left side, fit the cocking handle spring (716/2), the assembly formed by the cocking slide lever (713) and the cocking handle (730) and then the washer (715) onto the left end of the cocking slide lever stud (714) (left part of Fig. 12.2.c). The cocking handle spring (716/2) is supplied in the optional accessory kit (8997/2). When installing the cocking handle spring (716/2), ensure that its loop (a) fits correctly onto the cocking slide stop pin (724) and that its bent extremity fits correctly into the hole (b) provided in the cocking slide lever (713) (Fig. 12.2.c).

• Screw a nut (717), with its grooves facing outwards, onto the left end of the cocking slide lever stud (714) (Fig. 12.2.c). • Using the wrench UT 1180, tighten the nut (717) onto the cocking slide lever stud (714) (Fig. 12.2.c). Ensure that, at the end of this operation, one of the grooves of the nut (717) is perfectly aligned with the hole in the left end of the cocking slide lever stud (714).

• Using the pliers UT 1803, fit a split pin (719) into the aligned groove of the nut (717) and the hole in the left end of the cocking slide lever stud (714) (Fig. 12.2.c). • Using the pliers UT 1803, lock the split pin (719) by bending its 2 extremities (Fig. 12.2.c). • Install the cocking handle assembly (H1) onto the left side of the receiver frame (B1) and fix it by screwing the (shorter) screw (727) and the 2 (longer) screws (728) manually into position (Fig. 12.2.d). Please note that the (shorter) screw (727) is used at the lower rear side.

• From the inside of the receiver frame (B1), fit the 2 shoulder bolts (718) into position (Fig. 12.2.d). Ensure that the rectangular heads of the shoulder bolts (718) fit correctly into the corresponding recesses provided inside the receiver frame (B1), taking into account that both the recesses and the heads have chamfered edges which must be facing each other. Ensure that the left extremities of the 2 shoulder bolts (718) fit correctly into the corresponding holes in the cocking slide bracket (711).

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UT 1180

MI.50 M2HB QCB machine gun

718

719

717

UT 1803

H1

B1 728 H1

726 UT 1913

728

728

735 UT 1808 727

UT 1808

735

Fig. 12.2.e - Fixing the cocking handle assembly (H1) to the left side of the machine gun

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12.2. MOVING THE COCKING HANDLE ASSEMBLY (H1) FROM THE RIGHT SIDE TOWARDS THE LEFT SIDE OF THE MACHINE GUN (continued) • While holding the rectangular heads of the 2 shoulder bolts (718) in position with the fingers, screw a nut (717), with its grooves facing outwards, onto the left extremity of each shoulder bolt (upper left part of Fig. 12.2.e). • Using the wrench UT 1180, tighten the 2 nuts (717) onto the shoulder bolts (718) (upper left part of Fig. 12.2.e). Ensure that, at the end of this operation, one of the grooves of the nuts (717) is perfectly aligned with the hole in the left end of the corresponding shoulder bolt (718).

• For each shoulder bolt (718) and using the pliers UT 1803, fit a split pin (719) into the aligned groove of the corresponding nut (717) and the hole in the left end of the bolt (upper right part of Fig. 12.2.e). • Using the pliers UT 1803, lock both split pins (719) by bending their 2 extremities. • Firmly tighten the screws (727) and (728) with the screwdriver UT 1913 (middle part and lower left part of Fig. 12.2.e). • Using a wire (735) and the lock wire pliers UT 1808 at the rear side of the cocking handle assembly (H1), secure the (upper) screw (728) and the (lower) screw (727) (lower left part of Fig. 12.2.e). The wire should be installed so that, when tension is applied to it, this results in a tightening (and not a loosening) effort on the screws.

• Again using a wire (735) and the lock wire pliers UT 1808, secure the other screw (728) and the cocking slide stud (726) (lower right part of Fig. 12.2.e). The wire should be installed so that, when tension is applied to it, this results in a tightening (and not a loosening) effort on the screw and the stud.

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440 440

.

472

472

479

410 479

481

481

484

410 484 Fig. 12.3.a - Installation of the feed cover latch shaft (440) at the right side of the machine gun

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12.3. MOVING THE FEED COVER LATCH SHAFT (440) FROM THE LEFT SIDE TOWARDS THE RIGHT SIDE OF THE MACHINE GUN NOTE : Moving the feed cover latch shaft (440) from the left side towards the right side of the machine gun does not require new components. Please note that, when changing the machine gun from left-hand to right-hand feeding, it is not necessary to move the feed cover latch shaft (440) towards the right side of the machine gun.

Requirements : • UT 1803 (Half-round nose pliers) • Remove the feed cover latch shaft (440) and the feed cover latch (479) as described in § 9.4.6. • Fit the correctly oriented feed cover latch (479) into its mounting slot of the feed cover body (410) (left part of Fig. 12.3.a). Ensure that the pointed front part of the feed cover latch (479) fits correctly between the rear end of its spring (472) and the feed cover body (410).

• Align the hole in the feed cover latch (479) with the holes of its mounting slot of the feed cover body (410) and then, from the right side, insert the feed cover latch shaft (440) into the aligned holes, just far enough to secure the feed cover latch into position (left part of Fig. 12.3.a). When fitting the feed cover latch shaft (440), from the right side, back into position, a light pressure will be required on the feed cover latch (479), against the force of its spring (472), in order to correctly align the pin holes.

• Hold the washer (481) into position in the left notch of the feed cover body (410) and then push the feed cover latch shaft (440) into the washer and fully home (Fig. 12.3.a). • With the washer (481) in contact with the right side of the left notch of the feed cover body (410) and using the pliers UT 1803, fit the split pin (484) into the hole in the left end of the feed cover latch shaft (440) (Fig. 12.3.a). • Using the pliers UT 1803, lock the split pin (484) by bending its 2 extremities (right part of Fig. 12.3.a).

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MI.50 M2HB QCB machine gun

1500/1

X1

1520 1421

1521

1400

1522 545

d

1523 b

1431

1433

c

1431

e

551 (°)

b

548

f

1432

546

d

547

510

c

1415

1425 a

1434

542

3654 (°)

e f

543 544

549

541

3100 (Fig. 2.c.1)

(°)

a

500/4

3653 (Fig. 2.c.2)

3825

Fig. 13.a - The ‘anti-aircraft sights’-kit (500/4)

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MI.50 M2HB QCB machine gun

CHAPTER 13 : KITS 13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (Fig. 13.a) 13.1.1. Technical data Distance between ring and rear sights :

525 mm (20.7”)

Ring sight :

External diameter : 165 mm (6.5”)

Rear sight :

Double peep-hole for firing from 800 m (lower peep-hole) and 2000 m (upper peep-hole)

13.1.2. List of parts CAT n°

Description

Qty per unit

500/4 1400 1415 1421 1425 1431 1432 1433 1434 1500/1 510 541 542 543 544 545 546 547 548 549 551 1520 1521 1522 1523 3654 3825

Anti-aircraft sight kit > Ring sight assembly > > Front sight, ring sight > > Hexagonal nut, style 1 > > Bracket, ring sight > > Spring, ring sight > > Stop, removable, ring sight > > Pivot nut, ring sight > > Prevailing torque-type hexagonal nut > Rear sight for ring sight > > Base assembly, rear sight > > Knob, rear sight, windage screw > > Pin, knob, windage screw > > Plunger, rear sight, windage click > > Spring, windage click > > Adjusting screw, windage, rear sight > > Stop, rear sight leaf > > Scale, windage, rear sight > > Screw, scale, rear sight > > Spring, rear sight base > > Screw, sight base (°) > > Peep-hole assembly > > > Peep-hole > > > Hexagonal nut, style 1 > > > Base, peep-hole > Screw, externally relieved body (°) > Spring type straight pin, slotted (°)

1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 2 1 2 1 1 1 1 1 2

(°) The screws (551), the screw (3654) and the 2 spring pins (3825) will not be described in this chapter : they are the same and have the same function as the ones provided on the machine gun without ‘anti-aircraft sights’-kit (for more information, refer to the parts of this manual dealing with the receiver group [ 2 ] and the rear sight group [ 6 ]).

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.2. List of parts (continued) The following parts or assemblies cannot be ordered (separately) : a number has however been attributed in order to facilitate the descriptions throughout this maintenance manual :

N°

Description

X1

Ring sight

Qty per unit 1

13.1.3. Description The ‘anti-aircraft sights’-kit (500/4), which can be used for easier and quicker aiming (slightly less accurate but especially appropriate for aeronautical situations), consists of the following assemblies and components : - The 2 spring pins (3825) which are used to secure the ring sight assembly (1400) The 2 spring pins (3825) are not described in this chapter : they are the same and have the same function as the ones provided on the machine gun without ‘anti-aircraft sights’-kit (for more information, refer to the parts of this manual dealing with the receiver group [ 2 ]).

- The screw (3654) which is used to secure the rear side of the AA rear sight assembly (1500/1) The screw (3654) is not described in this chapter : it is the same and has the same function as the one provided on the machine gun without ‘anti-aircraft sights’-kit (for more information, refer to the parts of this manual dealing with the receiver group [ 2 ]).

- The ring sight assembly (1400) which mainly consists of the ring sight bracket (1425) provided with the assembly formed by the ring sight (X1) and its front sight (1415) The assembly formed by the ring sight (X1) and its front sight (1415) is secured to the front lugs of the ring sight bracket (1425) by means of the pivot nut (1433) onto which it can pivot. On its turn, the pivot nut (1433) is secured by means of the hexagonal nut (1434). The ring sight stop (1432), located between the front lugs of the ring sight bracket (1425) and held in a spring-tensioned position by means of the 2 springs (1431), ensures that the assembly formed by the ring sight (X1) and its front sight (1415) is correctly maintained at its lowered and raised positions. The ring sight front sight (1415) is screwed, from the bottom, into the ring sight (X1) and receives the hexagonal nut (1421). After the ring sight front sight (1415) has been adjusted correctly, it should be locked into position by means of the hexagonal nut (1421) (counterlocking nut).

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.3. Description (continued) - The AA rear sight assembly (1500/1) which consists of the rear sight base (510) onto which the following assemblies and components have been installed : • The peep-hole assembly (1520) which is secured by and can pivot on the rear sight windage adjusting screw (545) The peep-hole assembly (1520) consists of the peep-hole base (1523) provided with a threaded hole into which the peep-hole (1521) (provided with the hexagonal nut (1522)) is screwed. After the peep-hole (1521) has been adjusted correctly, it should be locked into position by means of the hexagonal nut (1522) (counterlocking nut). The rear sight windage adjusting screw (545) is screwed, from the right side, through the rear sight leaf stop (546), the rear sight base (510) and the peep-hole base (1523). The lateral position of the peep-hole assembly (1520) can be modified by turning the rear sight windage adjusting screw (545) by using the rear sight windage knob (541). This knob is fixed to the left end of the screw by means of the pin (542) and is used in combination with the windage click plunger (543) and its spring (544). The windage click plunger (543) and its spring (544), fitted into their housing in the rear sight windage knob (541), allow a precise positioning of the knob by generating a click each time the knob is rotated by 90°.

• The rear sight windage scale (547) which is fixed to the rear sight base (510) by means of the 2 screws (548) • The rear sight base spring (549) which ensures that the peep-hole assembly (1520) is correctly maintained at its lowered and raised positions The screws (551), which are used to secure the front side of the AA rear sight assembly (1500/1), are also part of the assembly. The screws (551) are not described in this chapter : they are the same and have the same function as the ones provided on the machine gun without ‘anti-aircraft sights’-kit (for more information, refer to the parts of this manual dealing with the rear sight group [ 6 ]).

13.1.4. Preparing the ring sight assembly (1400) and the AA rear sight assembly (1500/1) for use • Raise the ring sight assembly (1400) and the AA rear sight assembly (1500/1). • The peep-hole (1521) has a lower peep-hole set for 800 m and an upper peep-hole set for 2000 m.

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.5. Cleaning The following procedures should only be carried out in the very rare case of apparent soiling. Normally, a simple cleaning operation will be sufficient.

(a) Ring sight assembly (1400) • Completely disassemble the ring sight assembly (1400) by carrying out the different removal and disassembly procedures given in § 13.1.6. • Clean the disassembled components with a brush and/or a soft cloth. If necessary, use a soft solvent. In this case, ensure that the components are perfectly dry before reassembling them.

• Reassemble the ring sight assembly (1400) by carrying out the different reinstallation and reassembly procedures given in § 13.1.6. (b) AA rear sight assembly (1500/1) • Disassemble the AA rear sight assembly (1500/1) by carrying out the different removal and disassembly procedures given in § 13.1.7. It is not recommended to remove the rear sight windage scale (547).

• Clean the rear sight base (510) as well as the disassembled components with a brush and/or a soft cloth. If necessary, use a soft solvent. In this case, ensure that the components are perfectly dry before reassembling them.

• Reassemble the AA rear sight assembly (1500/1) by carrying out the different reinstallation and reassembly procedures given in § 13.1.7.

13.1.6. Disassembly and reassembly of the ring sight assembly (1400) (a) Removal and reinstallation of the ring sight assembly (1400) Requirements : • UT 2012 (Drift punch, dia. 3.5 mm, lg 27 mm) • UT 2111 (Hammer 250 g) • Using the drift punch UT 2012 and the hammer UT 2111, drive out the 2 spring pins (3825). NOTE : Once they have been removed, the spring pins (3825) must always be replaced by new ones ! • After the second withdrawal of the drift punch UT 2012, the ring sight assembly (1400) can be lifted up and off the receiver frame (B1). To reassemble, follow the above steps in reverse order, taking into account that the ring sight bracket (1425) should fit into the 2 outer grooves at the upper front side of the receiver frame (B1).

Maintenance manual

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.6. Disassembly and reassembly of the ring sight assembly (1400) (continued) (b) Removal and reinstallation of the assembly formed by the ring sight (X1) and its front sight (1415) as well as the ring sight stop (1432) Requirements : • 2 x UT 1114 (Open-end wrench 10 x 11 mm) • If necessary, UT 2012 (Drift punch, dia. 3.5 mm, lg 27 mm) • If necessary, UT 2111 (Hammer 250 g) • If necessary, remove the ring sight assembly (1400) as described in § 13.1.6 (a). Please note that this step is not absolutely necessary, as long as the necessary care is taken not to apply too much force when unscrewing the hexagonal nut (1434) (see further). When carrying out the following steps, it is recommended that the ring sight (X1) is at its lowered position.

• Using the 2 wrenches UT 1114, unscrew and remove the hexagonal nut (1434) from the left extremity of the pivot nut (1433). NOTE : Once it has been removed, the hexagonal nut (1434) must always be replaced by a new one ! • Taking into account that the assembly formed by the ring sight (X1) and its front sight (1415) as well as the ring sight stop (1432) and the 2 springs (1431) will be released, pull the pivot nut (1433) out of the right side of the ring sight bracket (1425). During this operation, it is recommended to push the ring sight (X1) slightly rearwards as the latter is subjected to the force of the 2 springs (1431).

• Separate the assembly formed by the ring sight (X1) and its front sight (1415) as well as the ring sight stop (1432) and the 2 springs (1431) from the ring sight bracket (1425). To reassemble, follow the above steps in reverse order, taking into account the following points : - When reinstalling the assembly formed by the ring sight (X1) and its front sight (1415), the lugs of the ring sight must be oriented as shown in Fig. 13.a. - Slightly lubricate the 2 springs (1431) and ensure that they correctly engage their housings in the ring sight stop (1432) and that the stop is oriented as shown in Fig. 13.a. - When fitting the pivot nut (1433), from the right side, back into position, a light rearward pressure will be required on the ring sight stop (1432), against the force of the 2 springs (1431). - The (new) hexagonal nut (1434) should be screwed firmly into position.

After any intervention on a sight assembly, the firing precision of the machine gun should be checked and, if necessary, adjusted as described in § 13.1.8.

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.6. Disassembly and reassembly of the ring sight assembly (1400) (continued) (c) Removal and reinstallation of the ring sight (X1) and its front sight (1415) Requirements : • • • •

UT 1108 (Open-end wrench 6 x 8 mm) 2 x UT 1114 (Open-end wrench 10 x 11 mm) If necessary, UT 2012 (Drift punch, dia. 3.5 mm, lg 27 mm) If necessary, UT 2111 (Hammer 250 g)

• Remove the assembly formed by the ring sight (X1) and its front sight (1415) as described in § 13.1.6 (b). • If the same ring sight (X1) and corresponding front sight (1415) will be used again, and in order to avoid the need to check and, if necessary, to adjust the firing precision of the machine gun after the reinstallation procedure, measure the distance between the top of the ring sight front sight and the bottom of the inner ring of the ring sight. • Using the wrench UT 1108, unscrew the hexagonal nut (1421) and then, taking care not to lose the nut, screw the ring sight front sight (1415) out of the ring sight (X1). To reassemble, follow the above steps in reverse order, taking into account the following points : - If the same ring sight (X1) and corresponding front sight (1415) are used again (see above), the distance between the top of the ring sight front sight and the bottom of the inner ring of the ring sight should be the same as the one measured before the disassembly. If the ring sight (X1) and/or the corresponding front sight (1415) are replaced by other ones, and before proceeding to § 13.1.8, it is recommended that the top of the ring sight front sight protrudes by 8.5 mm from the bottom of the inner ring of the ring sight. - The ring sight front sight (1415) should be locked into position by firmly tightening the hexagonal nut (1421).

After any intervention on a sight assembly, the firing precision of the machine gun should be checked and, if necessary, adjusted as described in § 13.1.8.

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.7. Disassembly and reassembly of the AA rear sight assembly (1500/1) (a) Removal and reinstallation of the AA rear sight assembly (1500/1) Requirements : • • • •

UT 1910 (Screwdriver 10 x 200 mm) UT 2030 (Center punch, dia. 6 mm) UT 2111 (Hammer 250 g) Requirements of § 10.5

• Remove the back plate assembly (600) as described for ‘field stripping’ in § 7.1. • Using the screwdriver UT 1910 and taking into account that it also secures the trigger bar stop assembly (B5) (also refer to § 9.2.13), take out the screw (3654) which secures the rear part of the AA rear sight assembly (1500/1) to the receiver frame (B1). Take into account that the head of the screw (3654) has been staked.

• Using the screwdriver UT 1910, take out the 2 screws (551) which secure the front part of the AA rear sight assembly (1500/1) to the receiver frame (B1). Take into account that the heads of the screws (551) have been staked.

• Lift the AA rear sight assembly (1500/1) up and off the receiver frame (B1). To reassemble, follow the above steps in reverse order, taking into account the following points : - Ensure that the positioning pins underneath the AA rear sight assembly (1500/1) fit correctly into the corresponding holes provided in the upper plate of the receiver frame (B1). - Reinstall the trigger bar stop assembly (B5) by proceeding as described in ‘10.5. Adjustment of the timing’. - After their reinstallation, secure the screws (3654) and (551) by staking their heads by using the center punch UT 2030 and the hammer UT 2111.

After any intervention on the trigger bar stop assembly (B5), the timing of the machine gun should be checked and, if necessary, adjusted as described in § 10.5.

After any intervention on a sight assembly, the firing precision of the machine gun should be checked and, if necessary, adjusted as described in § 13.1.8.

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.7. Disassembly and reassembly of the AA rear sight assembly (1500/1) (continued) (b) Removal and reinstallation of the peep-hole assembly (1520), the rear sight windage knob (541) and the rear sight windage adjusting screw (545) Please note that, for this operation, it is not necessary to remove the AA rear sight assembly (1500/1).

Requirements : • UT 1913 (Screwdriver 5.5 x 150 mm) • UT 2005 (Drift punch, dia. 1.4 mm, lg 15 mm) • UT 2111 (Hammer 250 g) NOTE : In order to facilitate the following disassembling (and reassembling) procedure, the machine gun can be fixed into a vice. When fixing the machine gun into a vice, use special clamps or a rag to avoid scratches.

• Using the drift punch UT 2005 and the hammer UT 2111, drive out the pin (542). NOTE : Once it has been removed, the pin (542) must always be replaced by a new one ! • After having withdrawn the drift punch UT 2005 and taking into account that the windage click plunger (543) and its spring (544) will be released, pull the rear sight windage knob (541) off the left end of the rear sight windage adjusting screw (545). • Using the screwdriver UT 1913 from the right side and taking into account that both the peep-hole assembly (1520) and the rear sight leaf stop (546) will be released, completely unscrew the rear sight windage adjusting screw (545) out of the rear sight base (510). During this operation, it is recommended to push down slightly on the peep-hole assembly (1520) as the latter is subjected to the force of the rear sight base spring (549).

• Lift the peep-hole assembly (1520) up and off the rear sight base (510). • If it did not come out yet, take the rear sight leaf stop (546) out of its hole in the right side of the rear sight base (510). To reassemble, follow the above steps in reverse order, taking into account the following points : - The rear sight leaf stop (546) should be fitted, from the outside and with its narrower end first, into its hole in the right side of the rear sight base (510). - When fitting the peep-hole assembly (1520) back into position, ensure that its graduation is facing rearwards. - When screwing the rear sight windage adjusting screw (545), from the right side, back into position, a light downward pressure will be required on the peep-hole assembly (1520), against the force of the rear sight base spring (549), in order to correctly align the screw holes. Ensure that the rear sight windage adjusting screw (545) fits correctly and completely into the hole in the left side of the rear sight base (510).

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.7. Disassembly and reassembly of the AA rear sight assembly (1500/1) (continued) (b) Removal and reinstallation of the peep-hole assembly (1520), the rear sight windage knob (541) and the rear sight windage adjusting screw (545) (continued) - When reinstalling the windage click plunger (543), first fit it onto its spring (544) and then insert this assembly, slightly lubricated and with the free extremity of the spring first, into the hole in the right side of the rear sight windage knob (541). - If it is difficult to insert the pin (542), use the drift punch UT 2005 to assist to align the holes in the rear sight windage knob (541) with the corresponding hole in the left end of the rear sight windage adjusting screw (545). - The pin (542) should not protrude after it has been reinstalled. - Before proceeding to § 13.1.8, it is recommended that the peep-hole assembly (1520) is centered inside the rear sight base (510). (c) Removal and reinstallation of the rear sight windage scale (547) Please note that, for this operation, it is not necessary to remove the AA rear sight assembly (1500/1).

Requirements : • UT 1903 (Screwdriver 3 x 75 mm) • Using the screwdriver UT 1903, take out the 2 screws (548) which secure the rear sight windage scale (547) to the rear sight base (510). • Remove the rear sight windage scale (547). To reassemble, follow the above steps in reverse order.

After any intervention on a sight assembly, the firing precision of the machine gun should be checked and, if necessary, adjusted as described in § 13.1.8.

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.7. Disassembly and reassembly of the AA rear sight assembly (1500/1) (continued) (d) Removal and reinstallation of the rear sight base spring (549) Please note that, for this operation, it is not necessary to remove the AA rear sight assembly (1500/1).

Requirements : • • • • •

UT 1903 (Screwdriver 3 x 75 mm) UT 1913 (Screwdriver 5.5 x 150 mm) UT 2004 (Drift punch, dia. 5 mm, lg 40 mm) UT 2005 (Drift punch, dia. 1.4 mm, lg 15 mm) UT 2111 (Hammer 250 g)

• Remove the peep-hole assembly (1520) as described in § 13.1.7 (b). • Remove the rear sight windage scale (547) as described in § 13.1.7 (c). • Using the drift punch UT 2004 and the hammer UT 2111, disengage the rear sight base spring (549) from its housing in the rear sight base (510). To reassemble, follow the above steps in reverse order taking into account that the rear sight base spring (549), which should be lightly lubricated before its reinstallation, should fit completely into its housing in the rear sight base (510). (e) Disassembly and reassembly of the peep-hole assembly (1520) Please note that, for this operation, it is not necessary to remove the AA rear sight assembly (1500/1).

Requirements : • • • •

UT 1108 (Open-end wrench 6 x 8 mm) UT 1913 (Screwdriver 5.5 x 150 mm) UT 2005 (Drift punch, dia. 1.4 mm, lg 15 mm) UT 2111 (Hammer 250 g)

• Remove the peep-hole assembly (1520) as described in § 13.1.7 (b). • Using the wrench UT 1108, unscrew the hexagonal nut (1522) and then manually screw the peep-hole (1521) (with the hexagonal nut) out of the peep-hole base (1523). • Manually unscrew and remove the hexagonal nut (1522) from the peep-hole (1521). To reassemble, follow the above steps in reverse order, taking into account that, before proceeding to § 13.1.8, it is recommended that there is a distance of 43 mm between the top of the peep-hole (1521) and the top of the peep-hole base (1523).

After any intervention on a sight assembly, the firing precision of the machine gun should be checked and, if necessary, adjusted as described in § 13.1.8.

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.8. Checking and adjusting the firing precision of the machine gun (a) Checking procedure NOTE : In order to increase the accuracy of the following checking procedure, it is recommended to use the machine gun on a tripod or to fix it in a fixing support such as a shooting adjustment device, ... In any case, eliminate the less accurate impact.

The firing precision should periodically be checked by proceeding as follows : • Turn the safety catch outwards so that the trigger (641) is no longer blocked into position and ensure that the bolt latch release (639) is unlocked and raised. • Using the (lower) ‘800 m’ peep-hole, aim the machine gun at a well-determined point on a safe target located at 50 m. • Fire 6 single shots and eliminate the less accurate impact. • At the target, check if the 6-1 impacts are situated within a square with a side of 30 cm. If so, directly proceed to the next step. If not, repeat the shooting procedure at least twice. If, during these next tries, the 6-1 impacts are still not situated within a square with a side of 30 cm, this indicates that the barrel (110) / (110/1) of the machine gun is showing signs of wear : replace the barrel and then restart this checking procedure.

• At the target, determine the mean point of impact (MPI). • If the MPI corresponds to an imaginary point approx. 220 mm above the point of aim, the firing precision is correct. If not, the firing precision should be adjusted as described in the following § 13.1.8 (b). (b) Adjustment procedure Requirements : • UT 1108 (Open-end wrench 6 x 8 mm) • UT 1903 (Screwdriver 3 x 75 mm) The AA rear sight assembly (1500/1) should be adjusted after each intervention (removal, disassembling, ...) on the sights of the machine gun. The ring sight front sight (1415) (with its top protruding by 8.5 mm from the bottom of the inner ring of the ring sight (X1)) should only be adjusted if the AA rear sight assembly (1500/1) does not allow a correct adjustment of the vertical position of the MPI. For the adjustment of the ring sight front sight (1415) proceed as described for the peep-hole (1521) taking into account that the elevation effect on the MPI is opposite.

The adjustment procedure should also be carried out if required by the checking procedure of the previous § 13.1.8 (a).

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MI.50 M2HB QCB machine gun

13.1. ‘ANTI-AIRCRAFT SIGHTS’-KIT (500/4) (continued) 13.1.8. Checking and adjusting the firing precision of the machine gun (continued) (b) Adjustment procedure (continued) Proceed as follows : • Check the firing precision of the machine gun as described in § 13.1.8 (a). If the MPI corresponds to an imaginary point approx. 220 mm above the point of aim, the following adjustment procedure should not be carried out. If not, carry out the following adjustment procedure.

• If a vertical correction of the MPI is required, proceed as follows : - Using the wrench UT 1108, unscrew the hexagonal nut (1522) in order to unlock the peep-hole (1521). - Manually, or using the wrench UT 1108, rotate the peep-hole (1521) by half turns in order to correct the vertical position of the MPI. In order to lower the MPI, turn the peep-hole (1521) in the clockwise direction (downwards). In order to raise the MPI, turn the peep-hole (1521) in the counterclockwise direction (upwards). Take into account that each half turn of the peep-hole (1521) will change the vertical position of the MPI by 3.6 cm on a target located at 50 m.

- Using the wrench UT 1108, firmly screw the hexagonal nut (1522) in order to lock the peep-hole (1521) back into position. • If a lateral correction of the MPI is required, proceed as follows : - Turn the rear sight windage knob (541) in order to correct the lateral position of the MPI. In order to move the MPI towards the right (left) side, turn the rear sight windage knob (541) in the (counter)clockwise direction when viewed from the left side. Take into account that each 90° turn of the rear sight windage knob (541) will generate a click and that each click corresponds to a change of the lateral position of the MPI by 2.5 mils.

- After this lateral correction of the MPI, it is most probable that the ‘0’ line on the rear sight windage scale (547) is not correctly aligned with the mark on the peephole base (1523). In such a case, correct the position of the rear sight windage scale (547) by proceeding as follows : - Using the screwdriver UT 1903, slightly loosen the 2 screws (548) which secure the rear sight windage scale (547) to the rear sight base (510). - Correct the position of the rear sight windage scale (547) and then tighten the 2 screws (548). • Check if the firing precision of the machine gun is now correct. If so, the adjustment is terminated. If not, repeat the adjustment procedure until a correct firing precision is obtained.

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MI.50 M2HB QCB machine gun

THIS PAGE IS INTENTIONALLY BLANK

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1080

1090

1091

Fig. 14.a - Accessories of the MI.50 M2HB QCB infantry machine gun (part I) Maintenance manual

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MI.50 M2HB QCB machine gun

CHAPTER 14 : ACCESSORIES 14.1. LIST OF ACCESSORIES (PART I) (Fig. 14.a)

CAT n°

Description

Qty per unit

1005 1080/1 1080/2 1090/2 1090/3 1091

Barrel periscopic inspection device (*) Cover, web, barrel (olive-green) Cover, web, barrel (sand-yellow) Cover, web, complete weapon (sand-yellow) Cover, cordura, complete weapon (olive-green) Pair of gloves, anti-heat

1 1 1 1 1 1

(*) Not illustrated

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160

164 4x

161

165

4x

163 162

400 8997/2

3829

716/2 3830

Fig. 14.b - Accessories of the MI.50 M2HB QCB infantry machine gun (part II) Maintenance manual

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MI.50 M2HB QCB machine gun

14.2. LIST OF ACCESSORIES (PART II) (Fig. 14.b)

CAT n°

Description

Qty per unit

160 161 162 163 164 165 400 8997/2 716/2 3829 3830

Flash-hider assembly > Cone, flash-hider > Ring, retaining, flash-hider > Segment, flash-hider > Screw, cap, hexagonal head > Nut, self-locking hexagonal, low height Machine, linking and delinking, cal. .50, M7 Inversion kit feed & cocking from L to R hand > Spring, helical torsion > Stripper, link > Stop, rear, cartridge

1 1 1 2 4 4 1 1 1 1 1

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1108

1100

3817 (Fig. 2.c.1) c c

1104

1103 1120 b b

1102

a

1117

a

1105

1106 1121/2

UT 1704

1121/3

Fig. 14.c - Accessories of the MI.50 M2HB QCB infantry machine gun (part III) Maintenance manual

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MI.50 M2HB QCB machine gun

14.3. LIST OF ACCESSORIES (PART III) (Fig. 14.c)

CAT n° 1100 1102 1103 1104 1105 1106 1108 1117 1120 1121/2 1121/3 UT 1704

Description

Qty per unit

CRB for MI.50 QCB > Washer, piston, expansion chamber > Piston, expansion chamber > Cover, holding, recoil booster > Plug CRB-QCB assembly > > Single coil spring washer strong serie > Ring, piston, combined recoil booster > Washer, tightening recoil booster cover > Parts, fixing recoil booster assembly > Discriminator for Blank Star cartridge > Discriminator, plastic-type cartridge > C-spanner 80/120

1 1 1 1 1 1 2 1 1 1 1 1

Tools UT 1703 C-spanner 50/80 (*) UT 2112 Hammer 300 g (*) OREA 779 Punch for washer (*)

1 1 1

(*) Not illustrated

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MI.50 M2HB QCB machine gun

500/1 (*) e

523

528

e

525

529 d

524

526 d

527

522

500/2

a

521

545 c

520

546

b

548

8997/1 (°)

a

551 510/2

505

547

340

542

b

2x c

541

543

408

549

544

2x

564 f

563 565 f

Fig. 14.d - Accessories of the MI.50 M2HB QCB infantry machine gun (part IV) Maintenance manual

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MI.50 M2HB QCB machine gun

14.4. LIST OF ACCESSORIES (PART IV) (Fig. 14.d)

CAT n°

Description

Qty per unit

500/1 500/2 510/2 520 521 522 523 524 525 526 527 528 529 541 542 543 544 545 546 547 548 549 551 563 564 565 505 8997/1 340 408

Rear sight assembly (metric graduation) (*) > Rear sight assembly > > Base assembly, rear sight > > Leaf assembly, rear sight > > > Leaf, rear sight 3 > > > Slide, rear sight > > > Knob, elevating screw > > > Screw, elevating, rear sight slide > > > Pin rear sight, elevating knob > > > Pin, retainer, rear sight, elevating screw > > > Nut, half, rear sight > > > Plunger, elevating, rear sight > > > Spring, plunger, elevating, rear sight > > Knob, rear sight, windage screw > > Pin, knob, windage screw > > Plunger, rear sight, windage click > > Spring, windage click > > Adjusting screw, windage, rear sight > > Stop, rear sight leaf > > Scale, windage, rear sight > > Screw, scale, rear sight > > Spring, rear sight base > > Screw, sight base > > Lock, rear sight base > > Spring, rear sight base lock > > Screw > Support, intermediate, telescope w/NATO base Kit Picatinny rail (°) > Safety washer scored > Hexagonal socket head cap screw, thin head

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 2 1 2 1 1 1 2 2

(*) Not applicable in case of a machine gun equipped with the ‘anti-aircraft sights’-kit (°) Same kit as the one listed in the table of § 14.5 and represented on Fig. 14.e

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MI.50 M2HB QCB machine gun

1500/3 (-)

1500/2 1521

1522

1520

545

a

1523

c

546 b

548

8997/1 (°)

a

551 510/2

505

547

340

542

b

2x c

541

543

408

549

544

2x

564 d

563 565 d

Fig. 14.e - Accessories of the MI.50 M2HB QCB infantry machine gun (part V) Maintenance manual

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MI.50 M2HB QCB machine gun

14.5. LIST OF ACCESSORIES (PART V) (Fig. 14.e)

CAT n°

Description

Qty per unit

1500/3 505 1500/2 510/2 541 542 543 544 545 546 547 548 549 551 563 564 565 1520 1521 1522 1523 8997/1 340 408

Dual AA rear sight with NATO support (-) > Support, intermediate, telescope w/NATO base > Dual AA rear sight assembly > > Base assembly, rear sight > > Knob, rear sight, windage screw > > Pin, knob, windage screw > > Plunger, rear sight, windage click > > Spring, windage click > > Adjusting screw, windage, rear sight > > Stop, rear sight leaf > > Scale, windage, rear sight > > Screw, scale, rear sight > > Spring, rear sight base > > Screw, sight base > > Lock, rear sight base > > Spring, rear sight base lock > > Screw > > Peep-hole assembly > > > Peep-hole > > > Hexagonal nut, style 1 > > > Base, peep-hole Kit Picatinny rail (°) > Safety washer scored > Hexagonal socket head cap screw, thin head

1 1 1 1 1 1 1 1 1 1 1 2 1 2 1 2 1 1 1 1 1 1 2 2

(-) Only applicable in case of a machine gun equipped with the ‘anti-aircraft sights’-kit (°) Same kit as the one listed in the table of § 14.4 and represented on Fig. 14.d

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MI.50 M2HB QCB machine gun

500/3 (-) 1500/2

1521

1522

1520

545

a

1523

The ring sight sighting system (1400/1) is not visually represented

c

546 b

548 3654

a

551 510/2 505/1

547

542

b

553

c

541

543 544

549 d

564 552

563 565 d

Fig. 14.f - Accessories of the MI.50 M2HB QCB infantry machine gun (part VI) Maintenance manual

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MI.50 M2HB QCB machine gun

14.6. LIST OF ACCESSORIES (PART VI) (Fig. 14.f)

CAT n°

Description

Qty per unit

500/3 505/1 552 553 1400/1 1500/2 510/2 541 542 543 544 545 546 547 548 549 551 563 564 565 1520 1521 1522 1523 3654

Kit rear sight, ring sight (-) > Support, intermediate, ring sight > Lockwire MS 9226-04 L 300mm > Screw, securing > Ring sight sighting system > Dual AA rear sight assembly > > Base assembly, rear sight > > Knob, rear sight, windage screw > > Pin, knob, windage screw > > Plunger, rear sight, windage click > > Spring, windage click > > Adjusting screw, windage, rear sight > > Stop, rear sight leaf > > Scale, windage, rear sight > > Screw, scale, rear sight > > Spring, rear sight base > > Screw, sight base > > Lock, rear sight base > > Spring, rear sight base lock > > Screw > > Peep-hole assembly > > > Peep-hole > > > Hexagonal nut, style 1 > > > Base, peep-hole > Screw, externally relieved body

1 1 1 2 1 1 1 1 1 1 1 1 1 1 2 1 2 1 2 1 1 1 1 1 1

(-) Only applicable in case of a machine gun equipped with the ‘anti-aircraft sights’-kit

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MI.50 M2HB QCB machine gun

1060 1040

1010 1020

1075

1032

1071

1031

1073

1050 1072

UT 2012 OREA 94

ACCE895 ACCE895/1

Fig. 15.1.a - Tool kit for the MI.50 M2HB QCB infantry machine gun (1000) and (1000/1) Maintenance manual

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CHAPTER 15 : TOOLS AND GAUGES 15.1. TOOLS 15.1.1. Tool kit for the MI.50 M2HB QCB infantry machine gun (1000) and (1000/1) (Fig. 15.1.a)

CAT n° 1000 1010 1020 1031 1032 1040 1050 1060 1071 1072 1073 1075 ACCE895 OREA 94 UT 2012 1000/1 1010 1020 1031 1032 1040 1050 1060 1071 1072 1073 1075 ACCE895/1 OREA 94 UT 2012

Description Complete tool kit n° 2 QCB, fixed timing (olive-green) > Cleaning rod > > Handle assembly > > Section, cleaning rod > > Swab, holder, section, cleaning rod > Brush, cleaning, complete, chamber > Complete barrel cleaning brush > Brush, cleaning, firing pin hole, cal .50 > Rod cleaning for firing pin hole > Cleaning rod > Ruptured case extractor > Handle, bolt (auxiliary use only) > Roll, tool (olive-green) > Oil can, complete with small chain painted > Drift punch, dia. 3.5 mm, lg 27 mm Complete tool kit n° 2 QCB, fixed timing (sand-yellow) > Cleaning rod > > Handle assembly > > Section, cleaning rod > > Swab, holder, section, cleaning rod > Brush, cleaning, complete, chamber > Complete barrel cleaning brush > Brush, cleaning, firing pin hole, cal .50 > Rod cleaning for firing pin hole > Cleaning rod > Ruptured case extractor > Handle, bolt (auxiliary use only) > Roll, tool (sand-yellow) > Oil can, complete with small chain painted > Drift punch, dia. 3.5 mm, lg 27 mm

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MI.50 M2HB QCB machine gun

OREA 235

OREA 269

OREA 228

OREA 554 OREA 270

OREA 574

OREA 558

OREA 721

OREA 722

OREA 742

OREA 806 OREA 800 OREA 801 (-)

OREA 798 (*) OREA 802

OREA 807

Fig. 15.1.b - Separate OREA for the MI.50 M2HB QCB infantry machine gun Maintenance manual

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MI.50 M2HB QCB machine gun

15.1. TOOLS (continued) 15.1.2. List of separate OREA (Fig. 15.1.b) CAT n° OREA 228 OREA 235 OREA 269 OREA 270 OREA 554 OREA 558 OREA 574 OREA 721 OREA 722 OREA 742 OREA 798 OREA 800 OREA 806 OREA 801 OREA 802 OREA 807 OREA 848

Description Wrench for ring guide, barrel MI.50 Screwdriver 13x3.8 (hexagonal tip) modified Rod, firing pin spring Wrench, nut, bolt latch rod Wrench, back plate handle screw Tool, assembling, bolt latch, .50 machine gun Tool, MI.50 buffer spring Center punch, flat-end Center punch, round-end Tooling for sleeve support, barrel Drift, 1.2x10mm dia. (*) Bush for OREA 801 Tip and blade assembly, screwdriver > Tip, screwdriver, bladed (-) > Blade, screwdriver, spare 801 > Spring type straight pin, slotted Riveting clamp depressor, breech, lock (°)

(*) Not applicable in case of a machine gun equipped with the ‘anti-aircraft sights’-kit (°) Not illustrated (-) Not separately available as a spare part

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MI.50 M2HB QCB machine gun

15.1. TOOLS (continued) 15.1.3. List of UT (not illustrated) CAT n° UT 1039 UT 1110 UT 1175 UT 1180 UT 1184 UT 1304 UT 1425 UT 1621 UT 1802 UT 1803 UT 1808 UT 1903 UT 1910 UT 1913 UT 2003 UT 2004 UT 2005 UT 2006 UT 2008 UT 2010 UT 2012 UT 2030 UT 2111 UT 2203 UT 2301 UT 2322 UT 2442

Description Combination wrench 1 1/8” Open-end wrench 7 x 9 mm Open-end wrench 1/2 x 9/16” Open-end wrench 5/8 x 3/4” Open-end wrench 13/16 x 7/8” Straight box wrench 12 x 13 mm Bar, dia. 6 mm Hexagonal key 1/8” Cutting pliers Half-round nose pliers Lock wire pliers Screwdriver 3 x 75 mm Screwdriver 10 x 200 mm Screwdriver 5.5 x 150 mm Drift punch, dia. 3.9 mm, lg 50 mm Drift punch, dia. 5 mm, lg 40 mm Drift punch, dia. 1.4 mm, lg 15 mm Drift punch, dia. 2.4 mm, lg 21 mm Drift punch, dia. 1.9 mm, lg 25 mm Drift punch, dia. 2.9 mm, lg 40 mm Drift punch, dia. 3.5 mm, lg 27 mm Center punch, dia. 6 mm Hammer 250 g Feeler gauge Torque wrench Screwdriver socket, torque wrench, 1/2” Twist drill, dia. 5.1 mm

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MI.50 M2HB QCB machine gun

15.1. TOOLS (continued) 15.1.3. List of UT (not illustrated) (continued) For the flash-hider assembly (160) (also refer to § 14.2) : CAT n° UT 1173

Description Open-end wrench 3/8 x 7/16”

For the NATO base rear sight assembly (500/1) and the kit Picatinny rail (8997/1) (also refer to § 14.4) : CAT n° UT 1609

Description Hexagonal key 6 mm

For the ‘anti-aircraft sights’-kit (500/4) (also refer to § 13.1) : CAT n° UT 1108 UT 1114

Description Open-end wrench 6 x 8 mm Open-end wrench 10 x 11 mm

For the NATO base AA rear sight assembly (1500/3) and the kit Picatinny rail (8997/1) (also refer to § 14.5) :

CAT n° UT 1108 UT 1609

Description Open-end wrench 6 x 8 mm Hexagonal key 6 mm

For the NATO base AA rear sight assembly with AA rear optical sight (500/3) (also refer to § 14.6) : CAT n° UT 1108 UT 1607

Description Open-end wrench 6 x 8 mm Hexagonal key 5 mm

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MI.50 M2HB QCB machine gun

OREA 255

OREA 797 1079/1 1079/2

1645 UT 2006 OREA 870 1610

1700

Fig. 15.2.a - FM/AM tools and gauges kit for the MI.50 M2HB QCB infantry machine gun (1000/2) and (1000/4)

Maintenance manual

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MI.50 M2HB QCB machine gun

15.2. GAUGES 15.2.1. FM/AM tools and gauges kit for the MI.50 M2HB QCB infantry machine gun (1000/2) and (1000/4) (Fig. 15.2.a)

CAT n° 1000/2 1079/1 1610 1645 1700 OREA 255 OREA 797 OREA 870 UT 2006 1000/4 1079/2 1610 1645 1700 OREA 255 OREA 797 OREA 870 UT 2006

Description Kit QCB, FM/AM armourer (olive-green) > Envelope, gauges (olive-green) > Headspace gauge .50 QCB > Fixed timing gauge > Device for adjustment headspace > Wrench, front sight > Adjusting screw > Drift-pin, placement pin, breech lock pin > Drift punch, dia. 2.4 mm, lg 21 mm Kit QCB, FM/AM armourer (sand-yellow) > Envelope, gauges (sand-yellow) > Headspace gauge .50 QCB > Fixed timing gauge > Device for adjustment headspace > Wrench, front sight > Adjusting screw > Drift-pin, placement pin, breech lock pin > Drift punch, dia. 2.4 mm, lg 21 mm

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OREA 255

OREA 797 1645 UT 2006

1610

1079/1 1079/2

OREA 870 G097

1700

Fig. 15.2.b - GM tools and gauges kit for the MI.50 M2HB QCB infantry machine gun (1000/3) and (1000/5)

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MI.50 M2HB QCB machine gun

15.2. GAUGES (continued) 15.2.2. GM tools and gauges kit for the MI.50 M2HB QCB infantry machine gun (1000/3) and (1000/5) (Fig. 15.2.b)

CAT n° 1000/3 1079/1 1610 1645 1700 G097 OREA 255 OREA 797 OREA 870 UT 2006 1000/5 1079/2 1610 1645 1700 G097 OREA 255 OREA 797 OREA 870 UT 2006

Description Kit QCB, GM armourer (olive-green) > Envelope, gauges (olive-green) > Headspace gauge .50 QCB > Fixed timing gauge > Device for adjustment headspace > Headspace selection gauge (0736675257) > Wrench, front sight > Adjusting screw > Drift-pin, placement pin, breech lock pin > Drift punch, dia. 2.4 mm, lg 21mm Kit QCB, GM armourer (sand-yellow) > Envelope, gauges (sand-yellow) > Headspace gauge .50 QCB > Fixed timing gauge > Device for adjustment headspace > Headspace selection gauge (0736675257) > Wrench, front sight > Adjusting screw > Drift-pin, placement pin, breech lock pin > Drift punch, dia. 2.4 mm, lg 21 mm

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MI.50 M2HB QCB machine gun

1671 GO

1650 (*)

NO GO

1673 NO GO

GO

1682

1695 (**)

1690 (**)

G028

MAXI

MINI

G093

Fig. 15.2.c - Separate gauges for the MI.50 M2HB QCB infantry machine gun Maintenance manual

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MI.50 M2HB QCB machine gun

15.2. GAUGES (continued) 15.2.3. List of separate gauges (Fig. 15.2.c) CAT n° 1650 1671 1673 1682 1695 1690 G028 G093

Description Bullet lead inspection (*) Gauge, checking, length, cartridge slot Gauge, checking, firing pin hole Gauge, checking, piston head Box, barrel gauges (**) > Gauge, calibrating, wear gauge (**) Firing pin protrusion (66-7-5105) Copper gauge for STL and CHR .50 barrels

(*) Only MI.50 M2HB QCB with chrome-plated barrel (**) Only MI.50 M2HB QCB with stellited chrome-plated barrel

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THIS PAGE IS INTENTIONALLY BLANK

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MI.50 M2HB QCB machine gun

CHAPTER 16 : NOTES

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