INTRODUCTORY NOTES
Aim
1. The aim of all mechanism lessons is to teach the soldier how the mechanism of the gun operates.
Instructors notes
2. Throughout all mechanism lessons, the instructor should make the fullest use of diagrams, skeleton locks and the gun itself in order to make the soldier see for himself how the mechanism operates. Stereotyped verbal descriptions should be, and can be, avoided by the good instructor.
Lesson 24. – “FIRING ACTION FIRST SHOT” AND “ACTION ON RECOIL”
A INSTRUCTORS NOTESClass and instructors
1. Squads under squad instructors. The squad will be seated half on each side of the gun and the instructor at the rear of the gun.
Periods
2. One 45-minute period.
Stores
3. Gun, tripod, condenser can and tube, liner and belt with drill cartridges, spare parts case, empty cartridge case, skeleton lock, wall diagrams and a pointer.
Preparation
4. The gun will be mounted with the other stores to hand. The wall diagrams when required will be put up where they can be seen by the squad.
B CONDUCT OF LESSONPreliminaries
5. Safety precautions.
Approach
6. Tell the squad the aim of all mechanism lessons (see Introductory Notes, para 1).
Firing action, first shot
7. Load the gun and raise the rear cover. Remove the trigger bar.
8. Tell the squad that they will now see how the first shot is fired. Tell them to watch the trigger bar lever and then raise the safety catch and press the thumb-piece. Point out that the pawl near the bottom of the firing lever pushes forward the bottom of the trigger bar lever. As this is pivoted near the centre, the top moves to the rear.
9. Place the trigger bar over the trigger bar lever and trigger. Tell the squad to watch the trigger bar and again press the thumb-piece. Point out that as the top of the trigger bar moves to the rear it engages in the projection of the trigger bar and draws it backwards. The front wall of the slot in the trigger bar pulls the tail of the trigger to the rear.
10. Hold up the skeleton lock so that the squad can see it and, controlling the firing of it, explain that as the trigger bar pulls the tail of the trigger to the rear, the nose of the trigger is released from the bent of the tumble. This allows the long arm of the lock spring to propel the firing pin forward on to the cap of the cartridge, thus firing the round.
11. Confirm the action in the lock using wall diagrams.
12. Question the squad on firing action, first shot.
Action on recoil
13. Place and empty cartridge case between the upper and lower projections of the gib. Half load and press the thumb-piece. Remove the fusee box and spring. Remove the outer casing muzzle attachment and the right slide. Raise the rear cover.
14. Tell the squad to watch the recoiling portions. The instructor should now move to the front of the gun and, stating that he is representing the forces which work the gun, push the muzzle cup back. The squad should then see the recoiling portions move about one inch. Point out that this backward movement would extend the fusee spring.
15. State that this backward movement is caused partly by recoil and partly by the effect of the muzzle attachment. Explain how the gases, which escape through the muzzle after the exit of the bullet, strike violently against the front cone and rebound on to the muzzle cup. This assists in driving the recoiling portions backwards. The gases then escape through the vents in the outer casing.
16. Question the squad on action on recoil.
Conclusion
17. Questions to and from the squad.
18. Sum up main points.
Lesson 25. – FIRST ACTION IN THE FEEDBLOCK
A INSTRUCTORS NOTESClass and instructors
1. Squads under squad instructors. The squad will be seated half on each side of the gun and the instructor at the rear of the gun.
Periods
2. One 45-minute period.
Stores
3. Gun, tripod, condenser can and tube, liner and belt with drill cartridges, spare parts case, an empty cartridge case, wall diagrams and a spare feedblock.
Preparation
4. The gun will be mounted with the other stores to hand. The wall diagrams will be put when required where they can be seen by the squad.
B CONDUCT OF LESSONPreliminaries
5. Safety precautions will be carried out.
Approach
6. Revise by question and answer “Action on Recoil.”
Then state that this lesson deals with the effect of the backward movement of the recoiling portions on the feedblock.
First action in the feedblock
7. The instructor should set up the gun by placing an empty case between the upper and lower projections of the gib. He should half load and press the thumb-piece, raise the front cover and remove the outer casing muzzle attachment and fusee box and spring.
8. Point out the recess in the prolongation of the left side plate and tell the squad to watch it, whilst the instructor (representing recoil) pushed back the muzzle cup. The recess will be seen to move to the rear.
9. Show the squad that the recess in the prolongation of the left side plate carries back with it the stud on the bottom lever of the feeblock. Explain and demonstrate how the bottom lever acting on the top lever causes the slide to move to the right.
10. The instructor should now place a drill cartridge in front of the bottom pawls of the spare feedblock. By operating the lower lever, he can show the squad how, when the slide moves to the right, the top pawls ride over the round and engage behind it. The bottom pawls prevent the round from slipping out of the feedblock.
11. Confirm the action of the feedblock using the wall diagrams.
12. Question the squad.
Conclusion
13. Questions from the squad.
14. Sum up main points.
Lesson 26. – BACKWARD ROTATION OF THE CRANK AND SECOND ACTION IN THE FEEDBLOCK
A INSTRUCTORS NOTES
Class and instructors
1. Squads under squad instructors. The squad will be seated half on each side of the gun and the instructor at the rear of the gun.
Periods
2. One 45-minute period.
Stores
3. Gun, tripod, condenser can and tube, liner and belt with drill cartridges, spare parts case, an empty cartridge case, wall diagrams, pointer and a spare feedblock.
Preparation
4. The gun will be mounted with the other stores to hand. The wall diagrams will be put when required where they can be seen by the squad.
B CONDUCT OF LESSONPreliminaries
5. Safety precautions.
Approach
6. Tell the squad that this lesson deals with the actions that take place in the recoiling portions during the backward movement, and with the effect this has on the feedblock.
Backward rotation of the crank
7. Revise briefly “Action on Recoil” and set up the gun as follows:–
Place as empty case between the upper and lower projections of the gib. Half load and press the thumb-piece. Remove the fusee box and spring and the outer casing muzzle attachment. Raise the rear cover.
8. Tell the squad to watch the crank handle and slowly push back the muzzle cup. Point out that the backward movement of the recoiling portions causes the tail of the crank handle to roll onto the roller, thereby rotating the crank. The rotation of the crank draws back the lock, in the same way as the human knee when bent draws back the foot. The rotation of the crank also causes the fusee to rotate and wind in the fusee chain, thereby further extending the fusee chain.
9. Tell the squad that at this stage the force of the recoil is expended, but the momentum of the lock, connecting rod, crank and crank handle causes the crank handle to continue rolling against the roller. Demonstrate by pressing on the knob of the crank handle, and point out that this rolling of the crank handle assisted by the pull of the fusee spring forces the whole of the recoiling portions forward, with the exception of the lock. Show how the lock continues its backward movement for a short distance before it joins in the general forward movement.
10. Question the squad.
Second action in the feedblock
11. Revise, by question and answer, the “First action in the feedblock” and set up the gun as follows:– Pull back the recoiling portions until the crank handle is vertical, close the rear cover and raise the front cover.
12. Force the recoiling portions forward by pressing the knob of the crank handle, causing it to roll on the roller and tell the squad to watch the recess in the prolongation of the left side plate. They will see that as the recoiling portions move forward, the recess moves forward, carrying with it the stud on the bottom lever. The bottom lever acting on the top lever will move the slide back to left.
13. Hold up the spare feedblock with a drill cartridge in front of the bottom pawls and the slide out to the right. Operate the lower lever by hand and show how the top pawls on the slide bring the cartridge in the belt to a position against the cartridge and bullet stops, ready to be gripped by the extractor. Explain how the belt as it moves to the left slides over the bottom pawls. These pawls are depressed as the cartridges pass over them, but rise again behind the fourth cartridge and prevent the belt from slipping back after the third round has been withdrawn by the extractor.
14. Confirm this with the aid of the diagrams.
15. Question the squad on the “Second action in the feedblock.”
Conclusion
16. Questions to and from the squad.
17. Sum up main points.
Lesson 27. – BACKWARD MOVEMENT AND COCKING OF THE LOCK
A INSTRUCTORS NOTESClass and instructors
1. Squads under squad instructors. The squad will be seated half on each side of the gun and the instructor at the rear of the gun.
Periods
2. One 45-minute period.
Stores
3. Gun, tripod, cendenser can and tube, liner with belt and drill cartridges, spare parts case, spare lock, skeleton lock and wall diagrams.
Preparation
4. The gun will be mounted with the other stores to hand. The wall diagrams will be put up when required where they can be seen by the squad.
B CONDUCT OF LESSONPreliminaries
5. Safety precautions.
Approach
6. Revise by question and answer “Action on Recoil” and set up the gun as follows:– Place an empty case between the upper and lower projections of the gib. Half load and press the thumb-piece. Remove the fusee box and spring. Raise the rear cover.
7. Draw the lock slowly backwards by rolling the crank handle on the roller and point out the movement of the lock to the squad. They will see that as the lock moves backwards, the extractor withdraws a live round from the feedblock and the empty case from the chamber. The horns of the extractor move along the cams until the cartridge is clear of the belt. Show that as the extractor arrives at the end of the cams, it would be forced down by the ramps on the rear cover and thus bring the live round into line with the chamber. State that the empty case would probably fall off at this stage.
8. Hold up the spare lock with a drill cartridge on the extractor and let the squad see that the cartridge is prevented from falling face of the extractor by the lower projection of the gib.
9. Question the squad.
Cocking the lock
10. Set up the gun again and state that the squad will now see what is happening inside the lock.
11. Draw the lock slowly backwards again by rolling the crank handle on the roller. Point out that the rotation of the crank causes the base of the connecting rod to rise and force the side levers head upwards.
12. Hold up the skeleton lock, and, lifting the side levers head by hand, show how the tumbler is rotated on its axis pin and the firing pin is thus drawn to the rear. Show that the long arm of the lock spring bears on the firing pin and the short arm on the nose of the trigger. Consequently the withdrawal of the firing pin compresses the lock spring.
Point out that as the tumble continues its rotation, the short arm of the lock spring forces the nose of the trigger over the bent of the tumbler. Bu the tumbler carries the firing pin still further to the rear until the sear, forced up by the sear spring, has its bent engaged in the bent of the firing pin. The firing pin is thus prevented from flying forward by the bent of the sear being engaged in the bent of the firing pin.
13. Confirm the mechanism of cocking the lock with the aid of the wall diagrams.
14. Question the squad.
Conclusion
15. Questions from the squad.
16. Sum up main points.
Lesson 28. – FORWARD MOVEMENT OF THE LOCK
A INSTRUCTORS NOTES
Class and instructors
1. Squads under squad instructors. The squad will be seated half on each side of the gun and the instructor at the rear of the gun.
Periods
2. One 45-minute period.
Stores
3. Gun, tripod, condenser can and tube, liner with belt and drill cartridges, spare parts case, spare lock and wall diagrams.
Preparation
4. The gun will be mounted with the other stores ready to hand. The wall diagrams will be put up when required where they can be seen by the squad.
B CONDUCT OF LESSONPreliminaries
5. Safety precautions.
Approach
6. Revise by question and answer the backward movement and cocking of the lock and set up the gun as follows:– Half load. Remove the fusee box and spring. Pull the crank-handle on to the roller and pull the belt to the left. Raise the rear cover.
Forward movement of the lock
7. Explain that when the force of the explosion is expended, the fusee spring takes command and by unwinding the fusee chain from the fusee rotates the crank.
8. Push the crank handle slowly on to the check lever and show how the rotation of the crank forces the connecting rod forwards and downwards, thereby causing the lock to continue its forward movement. Let the squad see how, as the lock travels forward, the extractor forces the live round into the chamber and then is moved upwards by the side levers acting on the extractor levers. Demonstrate the action of the side levers with the spare lock.
9. Using the spare lock, point out that as the extractor rises, the lower projection of the gib slides over the base of the round which has been moved into position in the feedblock. Show that the firing pin hole is thus brought opposite the cap of the live round in the chamber.
Seating for ejection
10. Remove the elevating joint pin and up-end the gun. Pull the crank handle on to the roller and place an empty case on the extractor opposite the firing pin hole.
11. Push the crank handle on to the check lever and show the squad how the empty case, if it has not fallen off before, will be forced off by the seating for ejection, as the extractor rises.
12. Lower the gun and replace the elevating joint pin.
Side plate springs
13. Point out the grooves in the sides of the extractor and explain that as the extractor reaches it highest position, the side plate springs engage in the grooves. This prevents the extractor from falling if there were no cartridges on the face as it begins its backward movement. If it did fall, the horns would foul the cams in the breech casing.
Locking of the breech
14. Repeat the forward movement of the lock and explain that the final movement of the connecting rod and side levers head causes the lock to be forced slightly further forward and closes the breech. With the spare lock, point out that during the final movement the steps on the side levers travel over the bents of the extractor levers and the base of the connecting rod goes below the horizontal. This locks the breech during the explosion of the charge.
Conclusion
15. Questions from the squad.
16. Questions to the squad.
17. Sum up main points.
Lesson 29. – SUBSEQUENT SHOTS AND END OF BURSTS
A INSTRUCTORS NOTESClass and instructors
1. Squads under squad instructors. The squad will be seated half on each side of the gun and the instructor at the rear of the gun.
Periods
2. One 45-minute period.
Stores
3. Gun, tripod, condenser tube and can, liner with belt and drill cartridges, spare parts case, skeleton lock and wall diagrams.
Preparation
4. The gun will be mounted with the other stores to hand. The wall diagrams will be put up when required where they can be seen by the squad.
B CONDUCT OF LESSONPreliminaries
5. Safety precautions.
Approach
6. Tell the squad that they know the actions that take place from the moment the thumb-piece is pressed until the second round is fed into the chamber. In this lesson they will see how the automatic fire of the gun is achieved and also how the gun stops when pressure is released from the thumb-piece.
Firing action, subsequent shots
7. Revise “Firing Action, First Shot” and set up the gun by half loading, raising the rear cover, removing the trigger bar and placing it over the trigger bar lever and trigger.
8. Draw back the lock, pull the belt to the left, and, controlling the trigger bar, allow the lock to go slowly forward. Explain that the firer, by maintaining pressure on the thumb-piece, holds back the trigger bar. Therefore each time the lock goes forward, the front end of the slot holds back the tail of the trigger before the lock is quite home.
9. With the skeleton lock cocked, push back the tail of the trigger and point out that by this means the nose of the trigger is prevented from engaging in the bent of the tumble.
Explain and demonstrate that when the lock is home, the side levers head depresses the sear, thus allowing the long arm of the lock spring to drive the firing pin on to the cap and fire the charge. State that the depression of the sear is so timed that the firing pin is not released until the lick is in the firing position.
10. Question the squad.
End of bursts
11. Set up the gun by fully loading, and place the trigger bar over the trigger bar lever and trigger.
12. Release pressure on the thumb-piece and show the squad that the trigger bar resumes its normal position.
13. Using the skeleton lock, point out that this allows the short arm of the lock spring to force the nose of the trigger against the tumbler.
Thus, as the lock comes forward and the sear is depressed, the nose of the trigger engages in the bent of the tumbler and the firing pin is held back.
14. Question the squad.
Conclusion
15. Questions to and from the squad.
16. Sum up main points and progress made with mechanism.
| <– Chapter 5 | Manual Index | Chapter 7 –> |
