.300 Browning Light Machine Gun mechanism

[Music] action of a machine the fire 450 rounds a minute is necessarily complex starting with loading you will be taken through all the stages of action in the Browning gun that produced this rapid rate of fire this retaining ball allows the round to be fed in and prevents it from slipping back the round is fed in by the feed slide with its feed pole their movement is controlled by the feed arm which operates within the feed way in the top of the breech block when the cocking handle is pulled to the rear for the first time the breech block is also pulled to the rear this causes the feed arm to pivot and push the feed slide out over the first round watch the movement again this action allows the feed ball to move over the round held by the retaining fall and grip it watch it again from immediately in front of the breech block all this happens when the cocking handle is pulled back now when the cocking handle is released the breech block moves forward and the round is carried across if we look at it again we shall see the feed pole pushing the first round hard up against the cartridge and bullet stops this round has dragged all the other rounds after it so that the second round is now held by the retaining ball the first round is now ready to be put into the chamber the mechanism for doing so is a transporter an attachment on the breech block on the inside of the cover of the gun is a spring with the cover closed this spring is in contact with the transporter forcing it downwards making the transporter gripped the first run when the cocking handle is pulled for the second time the breech block moves to the rear and as we see from this side view withdraws the first round now we'll watch the action again from the top and see the round leave the belt on the transporter a plunger moves along the top of the transporter cams and is kept in contact by the cover spring in the path of the plunger is a ramp which will force the plunger inwards let's see this happen from above the transporter is now free to be pressed down by its guide ramp thus the round is forced down and its rim is caused to enter the extractor grooves of the breech block the round itself is not yet in line with a firing pin hole the round is now clear of the feed way and could slide down the extractor grooves and drop off where it not for this transporter claw which continues to hold the round on the face of the breech block this completes one of the actions which occur on backward movement now let us put the breech block forward again to see another action on backward movement which happens at the same time on top of the gun is the cover cat below this is the top plate in which there is a recess herald within this recess is the tip of the cocking lever now when the breech block moves to the rear the cocking lever is forced over it's lower-end set in the slot of the firing pin has drawn the firing pin to the rear of the breech block thus compressing the firing pin spring against the sear spring pin the sear spring exerts an upward pressure the rear end of the spring holds the sear in its upper position the lower end of the sear has a recess called a bent this bent hooks round the firing pin bent to hold the firing pin at the rear of the breech block so much for the mechanism of the breech block itself on backward movement now the breech block must have a platform on which to move this is partly provided by the barrel extension which is screwed to the barrel in its forward position the breech block rests in the barrel extension to which it is locked by the breech lock here it is the breech lock fits into a recess in the breech block and is kept there by a cam in the floor of the gun body while the lock stands on the cam the barrel and barrel extension must move as one piece now behind the barrel extension is the lock frame this is fixed to the gun body and cannot move it acts as a platform to the breech block in its backward position a projection on each side at the front of the lock frame is in line with a corresponding slot on each side of the barrel extension the projections fit into the slots during backward movement when the breech block moves to the rear it takes the barrel extension with it until the lock is clear of the cam when the lock will be forced down by its trunnions striking the projections this disengages the barrel extension from the breech block now watch it again and this time you can see that the breech block moves independently to the rear while this was going on something else happened in the lock frame let us go back pivoted within the lock frame is the accelerator the lock frame also contains the barrel return spring if we remove the breech block we see the tee piece of the barrel extension and jutting from its side a stud the end of the barrel return spring rod wrists on this stud backward movement of the barrel extension rotates the accelerator and compresses the barrel return spring the backward movement of the breech block itself continues its rotation until the accelerator is stopped by this stud on the other side of the lock frame immediately this spring asserts itself and locks these two phases together thus locking barrel extension and lock frame together so much for the locking of lock frame and barrel extension let us take the breech block parklet forward again to watch something else which happens at the same time the backward movement of the breech block compresses a return spring here it is and the block comes to a halt against this buffer in the rear plate this completes our examination of the actions which take place during the backward movement of the breech block at the end of the backward movement the various components are in the following state there is a round on the face of the breech block ready to be fed into the chamber note that it is not opposite the firing pin hole in this position a round is held between the feed pole and the retaining pole here is the feed ball here the retaining ball the round is ready to be fed in into line with the transporter the breech block is cocked the tip of the cocking lever is forward therefore its lower end has drawn the firing pin to the rear where it is held by the sear the barrel extension and the lock frame are locked together you remember how this was done by the TPS and the accelerator cams and a very powerful return spring is fully compressed all these things have been brought about by pulling the cocking handle twice the first time the feed slide moves out over the first round in the belt which is held by the retaining ball and when the cocking handle is released the feed slide moves this round into position for transporting to the chamber the second time the cocking handle was pulled this round was gripped by the transporter and drawn to the rear by the breech block when the cocking handle is released for the second time the return spring has sets itself to drive the breech block violently forward now let us watch the forward movement of the breech block this involves several things that happen at the same time we'll examine each one separately first at the end of backward movement there was a round on the face of the breech block above the firing pin hole forward movement will cause the transporter plunger to be forced done by the underside of the cam which is fixed to the gun body thereby lining up the round between the firing pin hole and the chamber the unlocking of the barrel extension and lock frame is precisely the reverse action to the one that locked them further forward movement of the breech block from this position unlocks them let us go back to the locked position and examine the unlocking process in detail it is because the rear of the breech block on moving forward flicks the accelerators forward thus forcing their cams from the TPS so that the barrel returned spring can force the barrel extension forward let us stop a moment and see the effect of this movement of the barrel extension on the breech lock the breech lock on striking the breech lock em is lifted into the recess of the breech block so locking barrel extension and breech block together let us look at the gun from above and watch the effect of this forward movement on the feed mechanism we see the feed slide move across it carries with it the rond which was gripped by the feed pole on backward movement if we remove the feed slide we see that this round is lined up against the cartridge and bullet stops read here for the transporter the transporter is guided to follow the cams by its stud and rises to grip the next round while the breech block puts the first round in the chamber to digress for a moment should the transporter fail to withdraw this round when it is against this stop there is a feed pole extension which prevents the feed ball operating since the extension rides over the round which was not withdrawn you will remember that when the round is withdrawn the feed ball extension is free to drop in the gap and is no hindrance to the operation of the feed ball but to continue let us imagine that the transporter has gripped the round and around is now in the chamber at this stage we have the breech block fully forward the gun is ready to be fired this calls for a trigger the forward end of the trigger fits into the sear the forward end has two small cams here and here this is the cam surface of one of them these cams correspond with cams on the inside of the base of the sear here is one of them and here is the other let us watch the forward movement again and this time from the side and inside the breech block the top of the cocking lever is progressively turned to the rear remember its lower end fits in the firing pin which is held by the CR bent in a defect in the sear sear spring or firing pin might allow the firing pin to fly forward prematurely but the round cannot be struck at this point because the firing pin is held by the lower end of the cocking lever the movement of the cocking lever itself is controlled by the recess in the top plate thus the round could not be fired until the breech block was forward and the breech locked however if we continue provement under normal conditions we find that the sear is drawn along the trigger until the cams become engaged only now can the gun be fired by lifting the tail of the trigger which draws the sear down and frees the firing pin let us examine how this automatic firing takes place first the round within the chamber notice the round does not fit the chamber tightly but on being struck by the firing pin a high pressure of gas is released but is felt in all directions and expands the case to a tight fit this seals the chamber and prevents the gases which forced the round along the barrel from leaking into the gun body this pressure is felt equally on the face of the breech block causing recoil stopping the recoil here shows us at the breech block barrel and barrel extension are locked together and recoil as one piece recoil is assisted by a device at the front of the barrel casing the end of the barrel and the cone form a small chamber let's watch the path of the bullet through the cone let's stop while the bullets here it partially seals the cone the pressure of gases builds up behind the bullet therefore the cone is under pressure the only part free to move is the barrel which slides in the casing thus assisting recoil when the bullet leaves the cone gas pressure subsides in the barrel the barrel and barrel extension and the breech block recoil about half an inch while still locked together giving the bullet time to leave the barrel only then can the breech be unlocked so that the breech block can continue its recoil independently assisted by a sharp flick from the accelerator clause as they rotate to lock the barrel extension and lock frame together now let us put the breech block forward again to see another simultaneous action of recoil in the chamber is an empty case which has to be replaced with a live round the empty case is held on the face of the breech block in the extractor grooves at the same time a live round is gripped by the transporter recoil of the breech block withdraws both of them when the empty case is cleared of the chamber it drops off you will remember that during backward movement cocking takes place and the return spring becomes compressed it immediately asserts itself to drive the block forward the sear rides along to the trigger cams which are held down by keeping the trigger pressed stopping the action here to look inside we shall see the breech block become locked to the barrel extension only now can the sear go sufficiently far forward to pull itself down on the trigger cams thus firing the run automatic firing continues as long as the trigger is pressed all the ammunition lasts knowledge of the operation of the gun gives the gunner confidence and helps him to make effective this heavy volume of fire [Music]

Channel: AWM Collection

Views: 11,314

Rating: 4.9835391 out of 5

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Id: Ub4LMiM7ZOk

Length: 19min 25sec (1165 seconds)

Published: Wed Jun 07 2017