1951: Chapter 7 – Causes of Stoppages

INTRODUCTORY NOTES

Aim

1. The aim of all lessons in this chapter is to teach the soldier the cause of various stoppages.

Instructors note

2. The lessons in this chapter should not be taught until the squad have attained proficiency in IA and mastered the mechanism of the gun.

Lesson 30. – CAUSES OF FIRST POSITION STOPPAGES

A INSTRUCTORS NOTESClass and instructors

1. Squads under squad instructors. Squad seated on the right side of the gun with the instructor on the left of the gun and facing the squad.

Periods

2. One 45-minute period.

Stores

3. Gun, tripod, condenser can and tube, liner with belt and drill cartridges, covering for crank handle and landscape or natural target.

Preparation

4. Gun mounted with the other stores to hand.

B CONDUCT OF LESSONPreliminaries

5. Safety precautions.

Approach

6. Practise the squad in the IA for a Phase 1 stoppage.

7. State the aim of all stoppage lessons, (see Introductory notes, para 1).

Phase 1

8. Load the gun and press the thumb-piece. Raise the rear cover and draw back the lock slowly. Tell the squad that the cause of a Phase 1 stoppage is a weak charge which does not drive the recoiling portions fully to the rear. Consequently the extractor is not able to drop as the horns do not clear the cams. When the lock begins its forward movement, the horns foul the steps of the cams. The IA remedies this by completing the backward movement and allowing the extractor to drop.

Phase 2

9. Practise the squad in the IA for a Phase 2 stoppage.

10. Tell them that in this phase the extractor is not dropping due to a slow backward movement of the recoiling portions. The horns are therefore constantly fouling the cams. This slow backward movement may be caused by:-

(a) Too much weight on the fusee spring.

(b) Grit, or lack of oil in the working parts.

(c) Excessive packing.

(d) Worn barrel.

(e) Tight pockets.

(f) Friction due to frozen oil or water.

Explain that the IA remedies the stoppage as in Phase 1 and prevents it recurring by giving a faster backward movement. But stress that the stoppage is really due to bad maintenance.

Phase 3

11. Practise the squad in the IA for a Phase 3 stoppage.

12. Tell the squad that his stippage is caused by a weak or broken gib spring, which allows the cartridge to slide down the face of the extractor. When the lock moves forward, the bullet strikes the barrel block. A new lock will obviously remedy this stoppage.

Conclusion

13. Questions to and from the squad.

14. Further practice in IA for backward men.

15. Sum up main points.

Lesson 31. – CAUSES OF SECOND POSITION STOPPAGES

A INSTRUCTORS NOTESClass and instructors

1. Squads under squad instructors. Squad seated on the right side of the gun with the instructor on the left of the gun and facing the squad.

Periods

2. One 45-minute period.

Stores

3. Gun, tripod, condenser can and tube, liner with belt and drill cartridges, covering for crank handle and landscape or natural target.

4. The following prepared rounds are required:–

One separated case.

One telescoped round.

One damaged case.

Preparation

5. Gun mounted with other stores to hand.

B CONDUCT OF LESSONPreliminaries

6. Safety precautions.

Phase 1

7. Practise the squad in the IA for a Phase 1 stoppage.

8. Set up the gun for a Phase 1 stoppage and, as the crank handle is going forward the second time, explain that there is a damaged round on the face of the extractor which will not enter the breech. The position in which the crank handle will stop depends on which portion of the round is damaged. The IA remedies the stoppage by the removal if the damaged round.

Phase 2

9. Practise the squad in the IA for a Phase 2 stoppage.

10. Set up the gun and tell the squad that the front portion of the previous case has been left in the chamber. Consequently the live round cannot enter the breech fully. When the live round is withdrawn, the separated case is telescoped over its nose. The IA remedies this by the remeval of the telescoped round.

Phase 3

11. Practise the squad in the IA for a Phase 3 stoppage.

12. Set up the gun and explain that the cause of this stoppage is the same as in Phase 2, but that in this case the separated case remains in the chamber. The clearign plug will remove the separated case by expanding and gripping it firmly, thus remedying the stoppage.

Phase 4

13. Practise the squad in the IA for a Phase 4 stoppage.

14. Explain that a series of separated cases is caused by ineffective sealing of the breech. There is wear somewhere between the face of the extractor and the connecting rod, and as a result the lock does not go fully forward. When the round is fired, the cartridge case breaks and leaves a portion in the breech. A No. 1 and No. 2 washer placed on the connecting rod will close the breech properly and prevent a recurrence. State that at the first opportunity, the washers will be placed behind the adjusting nut.

Conclusion

15. Questions to and from the squad.

16. Further practice in IA for backward men.

17. Sum up main points.

Lesson 32. – CAUSES OF THIRD POSITION STOPPAGES

A INSTRUCTORS NOTESClass and instructors

1. Squads under squad instructors. Squad seated on the right side of the gun with the instructor on the left of the gun and facing the squad.

Periods

2. One 45-minute period.

Stores

3. Gun, tripod, condenser can and tube, liner with belt and drill cartridges, covering for crank handle and landscape or natural target.

4. One prepared round, a thick rimmed drill cartridge is required.

Preparation

5. Gun mounted with the other stores to hand.

B CONDUCT OF LESSONPreliminaries

6. Safety precautions should be carried out.

Phase 1

7. Practise the squad in the IA for a Phase 1 stoppage.

8. Set up the gun and raise the rear cover. Show the squad that a cartridge has been fed up slightly crosswise. Thus the base of the cartridge is not in line with the extractor grooves. The extractor has not been able to rise to its highest position as it has fouled the rim of the cartridge instead of accepting it smoothly in the grooves.

By easing the pressure on the lock and pulling the belt, the IA straightens the round and the crank handle can thus be knocked on to the check lever.

Phase 2

9. Practise the squad in the IA for a Phase 2 stoppage.

10. Tell the squad that grit or lack of oil may cause friction in the lock. There is not sufficient momentum to overcome this friction and consequently the extractor cannot rise to its highest position. Oiling will prevent a recurrence.

Phase 3

11. Practise the squad in the IA for a Phase 3 stoppage.

12. Set up the gun and show the squad that the base of a cartridge has fouled the mouth of the feedblock. When the slide started to move inwards, the top pawls were unable to carry the round into the feedblock. This is why the slide is out and the pawls rigid. State that the cartridge fouling the mouth of the feedblock may be due to:-

(a) Loose pockets.

(b) Liner not in line with the feedblock.

The IA releases the strain on the belt and enables the round to be straightened. Attention to points during firing will prevent a recurrence.

Phase 4

13. Practise the squad in the IA for a Phase 4 stoppage.

14. Set up the gun and raise the rear cover.

Explain that either the cartridge in the feedblock or the one on the face of the lock has a rim which is too thick to ride through the grooves of the extractor. Therefore the extractor cannot rise to its highest position and jams on the think rimmed cartridge.

The IA remedies this stoppage by releasing the extractor and allowing the removal of the thick rimmed cartridge.

Conclusion

15. Questions to and from the squad.

16. Further practise in IA for backward men.

17. Sum up main points.

Lesson 33. – CAUSES OF FOURTH POSITION STOPPAGES

A INSTRUCTORS NOTESClass and instructors

1. Squads under squad instructors. Squad seated on the right side of the gun with the instructor on the left of the gun and facing the squad.

Periods

2. One 45-minute period.

Stores

3. Gun, tripod, condenser can and tube, liner with belt and drill cartridges, covering for crank handle and landscape or natural target.

Preparation

4. Gun mounted with the other stores to hand.

B CONDUCT OF LESSONPreliminaries

5. Safety precautions.

Phase 1

6. Practise the squad in the IA for a Phase 1 stoppage.

7. State that the cartridge in the breech is not fired owing to a misfire. Alternatively an empty pocket in the belt, which will result in an empty breech, amy cause this stoppage.

Phase 2

8. Practise the squad in the IA for a Phase 2 stoppage.

9. Tell the squad that the cap of the cartridge is not struck due to a broken or damaged firing pin or a broken lock spring.

Phase 3

10. Practise the squad in the IA for a Phase 3 stoppage.

11. State that a recurrence of Phase 1 stoppages is caused by play between the extractor face and the base of the round. As a result the cap of the cartridge is not struck sufficiently hard to fire the round. A No. 1 and No. 2 washer placed on the connecting rod will take up the play and remedy this.

Conclusion

12. Questions to and from the squad.

13. Further practice in IA for backward men.

14. Sum up main points.

Lesson 34. – CAUSES OF SPECIAL STOPPAGES

A INSTRUCTORS NOTESClass and instructors

1. Squads under squad instructors. Squad seated on the right side of the gun with the instructor on the left of the gun and facing the squad.

Periods

2. One 45-minute period.

Stores

3. Gun, tripod, condenser can and tube, liner with belt and drill cartridges, covering for crank handle, landscape or natural target and skeleton lock.

4. Two prepared thick rimmed drill cartridges are also required.

Preparation

5. Gun mounted with the other stores to hand.

B CONDUCT OF LESSONPreliminaries

6. Safety precautions.

Special A

7. Exercise the squad in the IA for a Special A stoppage.

8. State that the cause of this stoppage is that either the fusee or fusee spring is broken; hence the lock and crank handle will remain fully to the rear, because there is no force to draw them forward.

Special B

9. Practise the squad in the IA for a Special B stoppage.

10. Explain that this stoppage will be caused by either:–

(a) Damaged extractor grooves, which will not accept the base of the cartridge in the feedblock, or

(b) Broken gib or gib spring, which will not allow the upper projection of the gib to be depressed.

Both of these causes will result in the extractor jamming against the base of the cartridge in the feedblock and being unable to rise to its highest position. A change of lock will obviously remedy this.

Special C

11. Practise the squad in the IA for a Special C stoppage.

12. State that this stoppage is due to damage to any of the following parts of the feedblock:–

(a) Upper lever.

(b) Lower lever.

(c) Top pawls or spring.

(d) Bottom pawls or spring.

Damage to (a), (b) or (c) would result in the cartridges not being fed into the feedblock. Damage to (d) would mean that when the top pawls move to the right, the belt would slip back out of the feedblock.

The gun fires two rounds before stopping as there are two rounds on the face of the extractor.

Special D

13. Practise the squad in the IA for a Special D stoppage ie, “Runaway Gun.”

14. State that a “runaway gun” is caused either by:–

(a) Broken or worn nose of the trigger and bent of the tumbler, or

(b) The short arm of the lock spring being broken above the trigger axis pin.

15. Using the skeleton lock, show that either of these will result in the nose of the trigger not engaging the bent of the tumbler. Consequently, even though pressure is released from the thumb-piece, directly the lock goes forward and the side levers head depresses the tail of the sear, the firing pin will fly forward and fire the round in the breech.

Conclusion

16. Questions to and from the squad on the causes of any position stoppage.

17. Sum up main points.

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