Thompson Submachine Gun: Principles of Operation 1943 Restored

here is a casualty of war a tommy gun been knocked out of action and is headed for the repair shop this means there's one less weapon to use against the enemy until this gun is put in firing condition again how long does it take to get it back into action well that depends if you know the gun thoroughly and understand how it functions time can be cut to a minimum and that's the important factor when you're doing your job in the field so let's see what makes it tick the Thompson submachine gun caliber 45 model 1928 a1 is air cooled and blowback operated it can be fired either full automatic or semi-automatic the gun is simple light flexible and it's high firepower makes it very effective in short ranges it's a reliable friend in a tough spot in order to have a clearer picture of how the Tommy gun functions will cut away the side of the receiver and frame so we can see what the inside looks like to simplify our explanation of functioning will divide the firing cycle into three phases first the trigger movement this involves the trigger the disconnect er the sear lever and the sear and now the second phase the forward movement of recoiling parts this involves the receiver group the bolt group the recoil spring finally the third phase the rearward movement of recoiling parts which also involves the receiver and bolt groups and the recoil spring to load the bolt is drawn to the rear the safety is locked and the magazine inserted to fire unlock the safety and here we are ready to take up the first phase of functioning the action of the trigger mechanism we'll use an animated diagram and take it step by step notice that the forward part of the bolt has been cut out to show the hammer now watch the action of the trigger mechanism when you pull the trigger it turns on the trigger pivot this lifts the disconnect er up under the sear leaver which in turn pushes up the front end of the sear the seer rotates around its pivot and depresses the nose of the seer this lets the bolt go forward now let's follow these steps on the gun itself we're looking at the top of the frame it's removed from the receiver will slow up the action and take it step by step again the trigger is pulled it rotates on its pivot and lifts the disconnect or up under the sear lever as the sea level rises it lifts the front end of the sear at the same time the sear is rotating around its pivot and the nose of the sear is being depressed allowing the boat to move forward this brings us to the second phase the forward movement of recoiling parts after the bolt has traveled about an inch it strikes the cartridge which is held under the lip of the magazine it pushes the cartridge forward up the bullet ramp and into the chamber here's the same action on the gun from the right hand side the front end of the bolt strikes the cartridge and pushes it forward the cartridge is held straight until it has almost cleared the magazine the bullet ramp then guides it into the chamber when it's seated in the chamber the extractor snaps around the groove of the cartridge during the forward movement of the bolt the lock is cam down into the locking grooves of the receiver this occurs just before the boat reaches its extreme forward position the triangular-shaped hammer is located on the underside of the boat the lower point of the triangle strikes the front end of the receiver as the bolt travels forward the hammer pivots driving the firing pin into the primer of the cartridge and firing the round this brings us to the third and last phase of the firing cycle the rearward movement of the requiring parts here is our diagram again when the cartridge is fired it's fast burning powder produces maximum chamber pressure almost instantaneously this pressure drives the bolt back the Bulgin turn forces the lock back against the locking surfaces of the receiver now back to the real gun again notice the angle of the locking group you can see how the rearward pressure of the powder gases forces the lock back against these grooves that's how the bolt is locked in the forward position the receiver of this weapon is made of steel the lock is made of bronze the reason for this is the two metals tend to stick together helping to keep the bolt locked long enough for the projector to start on its way out of the barrel as the projector leaves the barrel the high chamber pressure is reduced this releases the pressure on the lock allowing it to move up and to clear the locking surfaces of the receiver the bolt can now move to the rear after the bolt has been unlocked the remaining gas pressure drives the boat to the rear compressing the recoil spring which cushion the shock of recoil and stores up power for the forward movement let's go back to the diagram again notice that we're on the left side of the gun now as the boat moves back the firing pin spring forces the firing pin away from the face of the bolt it also makes the hammer pivot around the hammer pin cocking the firing pin as the boat moves to the rear the empty cartridge case is withdrawn from the chamber by the extractor which is snapped around the groove of the cartridge the extractor holds the empty case on the face of the bolt until it hits the ejector which causes it to pivot and fly out through the opening here is the same action on the gun in slow motion watch the empty case pivot to the right and out when it hits the ejector as soon as the boat with the empty cartridge case has passed over the lips of the magazine a fresh cartridge is forced up into firing position by the action of the magazine spring there are two notches on the underside of the bolt the front Cyr notch and the rear sear not the sear may engage in either the front or rear sear notch depending on the force of the bolts rearward movement when the submachine gun is fired semi-automatic it fires a single shot with each pull of the trigger when it is fired full automatic it produces bursts of shots with each pull of the trigger the semi-automatic and full automatic action is controlled by the rocker and the rocker pivot to demonstrate we'll place the receiver and frame side-by-side the parts are in the same relative position as in the assembled gun in semi-automatic fire the rocker travels in the T grew on the underside of the boat when the point of the rocker reaches the end of the tea grew its forced forward bringing the rockers rounded part in contact with a disconnect er thus the disconnect er is forced out from under the sear lever the sear lever operates independently of the sear blocking the disconnect er when the bolt moves to the rear as soon as the sear notch is exposed the sear spring expands forcing the sear up to engage the boat contact between the trigger and the sear is reestablished when the trigger is released the trigger spring expands pivoting the trigger so that the disconnect er is lowered the disconnect er spring then expands and forces the disconnected to return to its position under the sear lever notice the rocker is thus returned to its upright position with the rocker pivot in this position the tommy gun will fire at the rate of about 600 rounds per minute it takes five seconds to empty a 50 round drum magazine the rocker pivot is of eccentric design at full automatic the rocker is low enough to allow the boat to move forward without striking the point of the rocker therefore the seer nose remains in its lowered position and the gun fires as long as the trigger is held or until the cartridges are expended now for the safety it works like this when the safety is turned toward the rear or safe position the rounded part of the safety fits into a groove on the sear and locks it in its uppermost position when it is set it fire the flat milled surface is in a position where the sear can rotate around its pivot remember that the safety cannot be turned when the bolt is forward the bolt has to be to the rear because the sear must be up in order to allow the rounded part of the safety to engage in the groove of the sear also remember that when the bolt is forward the drum type magazine cannot be inserted or removed you can clearly see that when the bolt is forward the front part blocks the path of the magazine now we'll draw the bolt back notice that the front part of the bolt is no longer in the way and the magazine can now slide in freely now for the trip here it is the trip functions only when the Bucks type magazine is used its purpose is to hold the bolt open the magazine is empty therefore saving time when changing magazines and increasing the firepower of the weapon when the last round is fired from the box type magazine notice that the bolt stays open that's the function of the trip here's how it works there's a fin on the back of the magazine follower as the magazine empties this spin rises up and with the last cartridge is pushed out of the magazine the fin strikes the trip when the trip rotates around the trigger pivot it pivots the disconnect er which compresses the disconnectors spring and holds the disconnect er forward of the sear lever this leaves the sear free to rotate as the bolt passes to the rear the nose of the sear is forced up by the sear spring and engages a sear notch on the boat this is what the fin looks like on the rear magazine follower remember that the trip works only when the box type magazine is used when the last cartridge is fired from the drum magazine the bolt will stay closed now for a brief review of some of the highlights functioning breaks down into three main parts the trigger action the forward movement of the recoiling parts and the rearward movement of the requiring parts now watch the complete firing cycle the trigger is pulled turning on its pivot the disconnect er is raised which in turn raises the forward part of the sear and sear lever he pressing the nose of the sear and allowing the bolt to move forward under tension of the recoil spring the bolt strips a cartridge from the magazine the cartridge is guided up the bullet Ram and loaded into the chamber the lock kiss-cam down into the locking recess of the receiver at approximately the same time the lower part of the hammer strikes the forward part of the receiver rotates and strikes the firing pin the firing pin is forced forward which in turn strikes the primer of the cartridge and ignites the powder charge pressure from the expanding gasses is transmitted through the cartridge case bolt and lock against the locking recesses in the receiver as the bullet leaves the barrel the pressure subsides releasing the lock this action retards unlocking as recoil starts the firing pin spring forces the firing pin to the rear and rotates the hammer to its original position this action withdraws the firing pin from the face of the bolt as the bolt continues to the rear the ejector strikes the base of the empty cartridge case tries it from the grip of the extractor and throws it out of the ejector opening the next cartridge is forced up into loading position by the magazine spring when the eccentric rocker pivot is turned to the single fire position the rocker is raised in the path of the bolt the rear of the t-slot strikes the rocker forces it forward forcing the disconnect are out from under the sear lever the sear lever operates independently of the sear blocking the disconnect er when a sear notch is exposed during the bolts rearward movement the sear spring expands forcing the sear up to engage the bolt when the rocker pivot is turned to the automatic position the rocker is lowered away from the path of the bolt the sear nose will remain depressed as long as the trigger is held to the rear the boat will move back and forth firing the weapon until the ammunition is expended or the trigger is released with a bolt to the rear the safety can be turned from the firing position to the safe position locking the sear the purpose of the trip is to hold the bolt to the rear after the last cartridge has been fired firing automatic from the box type magazine when the last cartridge has been fired a projecting fin on the follower Rises rotating the trip this pulls the disconnect er out from under the seer lever with a disconnect er in this position the sear is free to engage one of the sear notches in the boat well that's the story of how the Thompson submachine gun functions with a clear picture of what makes it tick plus skill and practice you can make sure that the tommy gun will not fail when it's needed most you

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Keywords: Thompson Submachine Gun (Invention)

Id: bcBKnn8mGc0

Length: 22min 27sec (1347 seconds)

Published: Wed Apr 01 2015