US2548622A - Firing mechanism for submachine guns - Google Patents

Description

April m, 195% F. w. SAMPSON ET AL' FIRING MECHANISM FOR SUBMACHINE GUNS 3 Sheets-Sheet 1 Filed Aug. 14, 1946 April 10, 1951 F. w. SAMPSON ETAL FIRING MECHANISM FOR SUBMACHINE GUNS 3 Sheets-Sheet 2 Filed Aug. 14. 1946 J Mm 9v R bk mum Qt Q m I NM mi Hhn m k m6\ WW m Wm M Q\ O k%\ 3mm FR EDEH' IEK W E|AM Pscm,

EEDREELLHYgE,

April 10, 1951 F. w. SAMPSON ET AL FIRING MECHANISM FOR SUBMACHINE GUNS 3 Sheets-Sheet 3 Filed Aug. 14, 1946 3 m FREDERICKW 5AM F'SUN EEUREEILHYDE, aJmMH/wm 51W Patented Apr. 10, 1951 UNITED s'r'rss orr cri FIRING MECHANISM FOR SUBMACHINE. GUNS Application August 14, 1946, Serial No. 690,518

2 Claims. 1

This invention relates to an improved firearm of the type commonly referred to as a submachine gun. More specifically this invention relates to a magazine firearm of the blowback type which is capable of functioning as a semi-automatic weapon delivering single shots for each pull of the trigger or is capable of delivering sustained automatic fire in accordance with manual adjustments made at will by the firer.

The primary purpose of our invention is to provide a submachine gun adaptable to military needs which is characterized by economy of manufacture and reliability of functioning under all conditions of service.

' Additional objects of our invention are the provision of a firearm in which all parts are readily accessible for inspection, cleaning, or maintenance and one which utilizes parts of such simple, rugged design as torequire a minimum of maintenance attention.

Economy of manufacture has been accomplished primarily by the use of composite parts made up of simple shapeswhich require a minimum of fabrication and machining operations, while accessibility for inspection and repair is the result of a design which allows the parts of the enclosure and mechanism to be separated or taken down easily without tools.

A further important aim is to present an arm of this nature which. will be liable in a minimum degree to derangement by access of mud, sand, and other detritus, to the working parts, the receiver being of such nature and the arrangement of the action parts being such that a very secure enclosure is effected. With a magazine in place,

the weapon withstands severe mudand Sand tests.

The exact nature of the invention, as well as other objects, advantages, and features of invention will be apparent or understood from the following description and accompanying drawings, wherein:

Figure 1 is a right side elevation. of the assembled firearm, Slightly more than one quarter full size as at present designed.

Figure2 is a top view of the firearm.

Figure 3 is a partial, longitudinal vertical sectional view with the breech bolt in cocked position. Figure 3ia is a detail in Figure 3.

Figure 4 is a cross section onthe line 4' t of Figure 3.

Figure 5 is a partial, longitudinal horizontal section through the retracting slide.

Figures 6 and '7 are detail sections in the same plane as Figure 3, approximately three quarters 2 full size, showing the mechanism set to provide for semiautomatic and automatic fire respectively.

Figure 8 is a sectional view on the line 8-8 of Figure 6. I

Figure 9 is an enlarged, partial vertical. sectional view showing the bolt stop engaging the bolt after the last round has been stripped from the magazine.

Figure 10 is a View similar to Figure 9 showing the condition of the mechanism prior to removal of the last cartridge from the magazine.

Figures 11, 12 and 13 are partial enlarged, vertical sectional views in the same plane as Figure 3 showing three different positions of the safety cam and sear spring mechanism, respectively in safe condition, in firing condition, and in condition for disassembly.

Figure 14 isan exploded View of the safety cam and sear springs.

Figure 15 is an enlarged vertical sectional view showing the lock which retains the stock in as:- sembled relation to. the receiver.

Figure 16 isan enlarged cross sectional view on the line l'6-l'6 of Figure 3 through the change lever and magazine catch mechanism.

Figure 17 is anenlarged horizontal section a the magazine catch,. on the. line ll'--l'| of Figure '16. Figure 18 is a fragmentary View taken along the line le -48 of Figure 1.. Figure 19 is a. fragmentary view taken. along the line l9-l9 of Figure 18.

Referring to the drawing by characters of ref.- erence it will be seen that the firearm shown therein comprises a. receiver 1, having threadably attached thereto at its forward end a barrel 2 and having permanently ailixed to its rear end the tubular bolt housing tube 3. Slidably re;- ceived within the bolt housing 3 is the bolt. which comprises a reduced bolt proper 4 adapted. to be received in the central-bore 5. inv the receiver I and an inertia. block. 6. Although. these parts may be made integral. it is in. the interest. of economy to insert the small diameter piece 4 of the bolt into the larger inertia block and retain itv by any convenient means such as a shrink fit. The smaller portion 4' of the bolt is axially perforated and receives in the: perforation a firing pin 1, a tapered point 1" of which protrudes from the presser face 8 of the bolt. The pin is provided. with an. enlarged terminal head 9 engaging a rearwardly recessed surface in the bolt to serve as a locating stop. An: extractor Ill in the form of a fiat spring extends rearwardlly from. a conventional hook portion H: thereon beside the presser face 8 in a groove in the top side of the bolt and is provided with a shank portion l2 extending inwardly at right angles received slidably in a radial bore in the bolt in the rear of the firing pin. The engagement of the extractor shank with the firing pin retains the firing pin, and the extractor is in turn retained by a spring thrust plug- 13 which is provided with a protruding pointengaged in a recess I3 in the rear side of the extractor shank 12. A cap l4 to close the rear end of the bolt housing is provided with lugs I5 which have a bayonet joint engagement with blocks I5 and Iii fixed-at top and bottom of the bolt housing 3. Extending forwardly into the bolt housing is the spring guide rod I], which is provided with a forward portion [8 of reduced diameter. Received on the portion I8 is relatively stiff bolt buffer spring I9 and surrounding the buffer spring is the buffer tube 20 which is provided with a seat for the spring at its forward end, and with an outwardly flangedrear end 2! fitting slidingly in an axial bore in the block 6 and bolt 4. Engaged between the flanged end 2| and the spring thrust plug [3 in the bolt is the .bolt driving spring 22 which is relatively light by contrast with the bolt buffer spring l6. -It will be, obvious that as the bolt is driven rearwardly. the two springs will act in a series relation until the plug 13 contacts the end of the buffer tube 20 when the two springs will act independently or in multiple, so that the sum of their forces is manifest on the bolt. The relatively stiff buffer spring especially will cause a much greater retarding influence and stop the rearward movement of the bolt very quickly in this second stage of recoil. As the bolt returns toward battery position or to the cooked position :at which it is stopped by the sear, the heavy buffer spring will cease exerting its superior influence a short distance rearward of such cocked position as the thrust plug moves away from the end of the buffer tube, and allows the movement to. be completed with less spring force exerted, since the two again become serially effective.

I A stationary ejector 23 (Figure 3) is mounted in the left side of the receiver and extends into the axial bore 5 therein in position to engage the rear face of a cartridge 24 gripped by the extractor in the recoiling bolt and eject the same through the ejection port 25 at the upper right as the bolt moves rearwardly. A clearance cut "26, Figure 4, is provided in the left side of the bolt to allow the bolt to pass by the ejector as the bolt moves forwardly. By reference to Figures 18 and 19 it will be seen that the ejector mounting comprises a cylindrical body 21 integral with the ejector proper and received in a lateral bore in the wall of the receiver. Near the outer end of the body there is provided an eccentric flange 28 and the extreme outer end is provided with a screwdriver slot 29 or other convenient means of operation. An undercut slot 3|] is provided in the well of the hole through the receiver to receive the flange 28 at times and communicating therewith and with the outer face of the receiver is a clearance cut 3| of equal radius, capable of allowing the eccentric flange 28 portion of the ejector shank to pass into alignment with the undercut slot. When the shank has been inserted fully and rotated through nearly 180 degrees, it will be seen that the eccentric portion is engaged and stopped in the slot and that the ejector is secured against both longitudinal displacement and further rotary movement and retained against axial displacement in the bore. A light staking operation at 32 on the material of the receiver beside the body 21 at the slot 29 makes the assembly semi-permanent without preventing replacement which may be affected by forcibly rotating the ejector body with a screwdriver or other convenient tool back to the position with the flange in the clearance cut 3 I, and withdrawing the body 21. 7

The cap I4 closing the rear end of the bolt housing 3 is provided with a lug 32 engaging in known manner a recessed recoil plate 33 secured by a bolt or other convenient means to the stock 34 which is suitable inletted to receive the lower half of the cap, the bolt housing, the receiver and the barrel. A forward top hand guard 35 is provided with a metallic extension 33 received under a forwardly extending top flange 31 at the forward end of the receiver, and the guard is secured to the stock by a band 38 embracing both stock and guard and slipped onto them from the front. A depressible spring catch 39 on the right side of the stock releaseably retains the band against accidental removal.

Mounted in the stock is the trigger housing 40, which houses the trigger mechanism to be described in more detail hereafter, and also provides a base for the mounting of additional means for securing the stock and receiver in assembled relation. The last mentioned means comprise a rotary receiver-engaging lock 4| which is a cylindrical body journaled in the forward flange 40' of the trigger housing, headed at its lower end and provided with a spring arm 42 which is secured thereto and is provided with a detent 43 (Figure 3) normally engageable with a notch 44 (Figure 15) in the trigger housing. An annular groove 45 in the rotary lock receives the arms of a bifurcated bow spring 46 which applies spring pressure to the lock opposing downward movement of the look away from receiver engaging position. A pin 41 passing through the trigger housing is received in a notch 48 in the side of the lock to prevent removal of the lock and so shaped as to limit the rotational movement thereof. As best seen in Figure 15, the upper end portion of the rotary lock M has been substantially all cut away at one side of a substantially diametral line and the remaining upstanding portion is provided with a slightly angled undercut 49, which is substantially at right angles to said line, the overhang of which is adapted, upon rotation, to engage over a cooperating forwardly projected lug 50 formed on the lower side of the receiver I. The upperside of the cut 49 is inclined so that when the lock has been rotated into position in which the detent on the arm engages the notch 44 in the trigger housing the trigger housing will have been drawn upward into tight engagement with the bottom of the receiver and will be securely held until intentionally released.

As best seen in Figure 3, the bolt insertia block 6 is provided with a sear-engaging shoulder 5| adapted for engagement with the heel 52 of the sear 53 which is a lever of the first order pivoted On a pin 54 set in and across the trigger housing. A sear stop 55 is mounted in the trigger housing in position to engage the toe 56 of the sear and limit the movement of the sear under the impetus of spring means to be described. The trigger 5'! is the lower body of a two-piece member mounted to rock about a pin 58 set across the trigger housing. As seen in Figures 4, 6, and '7, a longitudinal channel 59 is formed in the top of the trigger and has slidable therein a tripper 60 projecting before and behind the trigger and having a rear depending seat lug 6| biased rearwa'rdly by a spring 62 to aposition in which therear endof the tripper engages beneath the toe 5B of the sear 53 at :the free position of the trigger. A longitudinal slot 63 extending transversely through the tripper received the trigger pin 58 therethrough to secure the tripper to the trigger while allowing a limited amount of sliding movement of the tripper against the action of the'spring 62'. A forwardly located trigger spring B-Ll acts against the underside of a cup plunger-'55 which bears against the underside of the forward end of the tripper, resisting movement of the trigger toward firing position.

As seen in Figures 3, 6, 8, and 16 thegun is set to deliver fire semi-automatically due to the position of a selector 51, the cylindrical shaft 66 of which is received revolubly in a transverse bore inthe trigger housing. The shaft has a central :notch forming a cam fiat 58 which, in one position, shown in Figure 6, is disposed in the rear of a depending cam hook-69 on the'forward end of the tripper. The fiat 68 subtends a chord of 'much less than 180 degrees in the transverse bore, so that it may, by rotation of the L-handle selector 6?, be rotated from a plane in the rear part of the bore to a plane in the forward part of the bore, and the hook 69 is shaped and adapted to heat released position of the trigger intermediately of these two planes, so'that the selector 'may be rotated from one said position to the other without disturbing the hook 69, the fiat clearing the lowerend of the hook when the fiat is at its lowermost position and the trigger in released position. However, with the flat 68 at its rear position, it is nearly vertical, but is inclined across the path of the hook 69 in the latters movement from upper to lower extreme positions. The hook initially rests against the upper part of the fiat, and if the trigger is pulled, the hook wipes against the flat and is thereby cammed forwardly.

It will be apparent that as the trigger is actuated the tripper will, by reason of the wiping engagementof the cam hook 69 with the selector, be drawn forwardly to such an extent as to pass from under-the toe of the sear just after the sear has been moved through a sufiicient angle to release the bolt to fire a round. The sear will then by a searspring to be described, immediately return to position to engage the inertia block as the latter is'driven rearwardly after the round has fired and it will not be possible to fire succeeding round until the trigger has been released to permit the tripper to reengage itself beneath the toe of the sear, and

the trigger again operated.

At the forward position of the flat 68 the hook is free to move downward without disturbance, and the fiat will lie so close to the hook as to prevent it from moving forwardly to clear the toe of the sear.

Figure? shows'the action of the firing mechanism when the selector has been rotated through 180 more or less into automatic fire position in which the fiat B8 is forward of the cam hook 58 of the tripper. In this position, as the trigger is operated the selector forces the tripper to remain in its rearmost position with regard to the trigger and the tripper cannot disengage itself from the toe of the sear. The weapon will, it is apparent, continue to fire as long as the trigger is depressed and the ammunition supply is not exhausted.

As shownin Figures 6 and 7' a'spring plunger 70 engages, alternatively, flattened portions H formed on opposite sides .of the selector to releaseably hold the selector in either of its two angularly. spaced operative positions. The cam hook of the tripper serves to .prevent withdrawal of theselector until removal of the tripper. The lower end of the spring plunger is .normally received in a clearance cut 13in the magazine latch 74 which projects below the magazine well it" of the trigger housing and servesasa stop to limit forward movement thereof. The magazine latch is provided with a finger engaging portion 17%" and is slidably received in suitable guide ways in the trigger housing and is impelled forwardly by a latch spring 15 into position to engage the magazine 16 which may be .conveniently of :the type shown in U. S. Patent 'No. 1,350,619 and commonly used with the well known Thompson submachine guns. The receiveris conventionally ported at T6 to receive'theend of themagazine, which has a spring follower H to yieldingly present the top cartridge in the path of the bolt.

It will be apparent that'removal of the selector will permit upwardremoval of the selector spring and plunger land that this will in turn permit the magazine latch 'andits spring to bewithdrawn forwardly from the front of the trigger housing, Which is readily accessibleat thispoint.

Figures 9 and 10 illustrate the operation of the mechanism functioning to hold the bolt in rearward position when the last round has been stripped from the magazine and fired. The magazine follower H is, as shown in the patentabove referred to, provided with a downwardly :and rearwardly extending finger 18 which upon removal of the last round from the magazineengages the forward arm of a trip lever 19 of the first order, pivoted on the trigger pin 58 and having its rear endengaging over and upon the upper surface of the forward arm 88 of an auxiliary sear 8! which is also a lever of the'first order mounted in side by side relation with the sear 53 upon the sear pin 54. A spring 82 is engaged .between'the trigger housing andthe arm 88, tending toelevate the latter and keep the rear arm L of the auxiliary sear lowered to clear the shoulder SI of the bolt. However, when the last round has been stripped from the magazine the finger to engage the shoulder 5! and stop forward movement of the bolt. The spring 32 is relatively light and exerts insufficient force to disengage the auxiliary sear as long as the bolt return spring urges the shoulderl forwardly against the auxiliary sear. It is thus possible to remove an empty magazine and replace it with afull one without closing the bolt. To release the auxiliary sear it is necessary that the bolt be drawn slightly to the rear and then allowed to return into engagement with th regular sear.

Safety of the arm is providedfor by the mechanism shown'in detail in Figures 11, 12, 13, and 14. It will be noted that the sear spring 83 urges the sear spring plunger 84 upwardly against the lower face of theheel end of the scar and that .theJsafetyleVer:8l-onithe outer-end of the shaft 86 has been swung through 90 to the front, turning the shaft 86 to a position in which there is opposed to'the plunger a recess 88 in the' side of the shaft which receives the end of the plunger stem and allows firing movement of the sear. It will also be noted that in either of the positions just mentioned the retainer 85 is forced into en gagement with a respective flattened portion 89 on the shaft 96 by the action of a retainer spring 90, which is engaged between the retainer and a downwardly facing annular shoulder 9! in the trigger housing.

By reference to Figure 13 it may be seen that when the safety lever has been turned rearwardly there are no recesses opposed to the retainer 85, and the safety may be removed by sliding it laterally from the trigger housing. It then becomes possible to remove the plunger 84, spring 83, retainer'85 and spring 90 downwardly through the hole 92 in the lower portion of the housing; or, alternatively, the plunger 84 and spring 83 may be removed upwardly after removal of the sear.

It may be noted that in the safe position, the safety lever 81 extends downwardly in a plane approximately normal to the axis of the arm, and that inthis position it interferes with gripping of the pistol type grip 93 to such an extent that the attention thus gained makes it unlikely that there will be any attempt to fire the weapon. It may be further noted that when the trigger housing is secured in its recess in the stock the transverse trigger and sear pins will have their end portions covered by the sidewalls of the recess in the stock. It is therefore unnecessary to provide any special means of securing these pins and the entire mechanism may be stripped with facility when the trigger housing is removed from the stock. However, for inspection, cleaning and other routine maintenance, it is not necessary that the trigger housing be removed from the stock sinc the whole mechanism is readily accessible with the receiver and bolt housing removed from the stock.

The arm is conveniently cocked for the firing of the first round (or in case of failure to function automatically) by operation of the cocking handle 94 projecting from the right side of the tubular bolt housing. By reference to Figures 4 and 5 it will be seen that the handle 94 is formed with an integral bar 95 extending longitudinally rearward within the bolt housing 3, the bolt inertia block 6 being channelled at 96 to receive the major part of the bar freely therein as at 96 so that the bolt is feathered thereby at the rear part. The handle 94 projects laterally through, and is guided by a slot 91 formed in the side of the bolt housing 3. The forward end of the bar 95 is formed with an inner shoulder 98 projected horizontally inward before the path of the block 6, and the latter is recessed at 98' to receive this lug when the block is at the forward limit of its movement with the bolt proper, this being termed in battery. At this position, the forward part of the block (which is circumferentially relieved to enter within an annular flange 99 at the rear end of the receive I) abuts the breech face I00 of the receiver within said flange and the block is recessed suitably to receive the lug therein. The bar and handle may be termed a cockin slide. The forward inner end part of this slide is recessed to accommodate a part of the receiver in which a radial spring-pressed bullet fastener I0! is mounted, the plunger of which is convex on its outer end and adapted to snap into and out of a small indentation I02 or dimple in the slide when the latter is moved to' or from its forward limit of movement. The .bar is utilized as a closure for the slot 91, lying close against the edge portions of the housing 3 beside the slot 91 when the slide is forward, to prevent entry of dirt into the mechanism;

The bar 95 is bored from its rear end forwardly for a major part of its length, and provided with a telescoping rod I02 which confines in the bore a coil spring I03. The rod is limited in its rearward movement by being relieved at one side, and a cross pin I04 set through the bar, lying in the space afforded by the relieved part I05 of the rod and serving as a stop to outward movement 'of the rod. The inner side of the bar is cut away from top to bottom, from the end forwardly a distance, as at I06, and secured to the inner side of the rod there is a thin plate I91, extending from the end of the rod forwardly but stopping short of the forward limit of the cut away part I96, so as to permit slidin of the rod forward as required. The thickness of the plate ID! is less than the radial depth of the channel 98 in the side of the bolt body 6, so that when the bolt is at an intermediate position in its reciprocation, parts of both the bar 95 and plate ID! are engaged in the channel. The plate it! also extends slightly forward of the rear end of the bar when the rod is fully extended by its spring, so that the upper and lower parts of the bar abutting the plate prevent its rotation around the axis of the rod. In this way when the bolt is operating by recoil, and passes rearwardly of the rear end of the bar 95, it is still held against rotation by the plate I01 and will be guided thereby in counterrecoil so as to prevent interference by engaging end edges of the bar. When the cocking handle is drawn rearwardly the cock the firearm, the rod I02 will contact the closing cap I4 of the bolt housing and the sprin 91 will be compressed. If the cocking handle is abruptly released in its rear position the bolt will be retained by engagement with the sear and the spring I03 will impel the cocking handle forwardly to a position in which it will be engaged and retained by the latch l0]. If the cocking handle does not immediately become latched at its forward position, the next firing operation of the bolt will carry it forward to fully latched position, where it will remain during normal subsequent semi-automatic and automatic operation of the weapon.

It should be noted that the portion of the cocking handle without the slot 91 is slightly enlarged, so that it cannot be pressed inwardly through the forward part of the slot, and the part of the handle in the slot is of sufficient extent longitudinally of the weapon to support the slide in the proper operatin position. The rear end of the slot, however, is enlarged as at H l to conform to the shape of the handle 94, and permit the same to be pressed inwardly into the bolt housing 3 when the bolt block 6 is out of the way. This enables dismounting of the cocking slide without tools, as will appear.

It may be seen that the stock 34 here provided is quite straight, very close to, and in its major part parallel and nearly concentric with the axis of the barrel 2. This is made possible by the fact that the line of recoil forces and the reaction from the butt plate 33 are in very close alignment. In consequence, there is a negligible force couple tending to cause the gun to climb during automatic firing. For convenience in operation the front slight I96 and rear sight l0] are substantially raised to place the line of sight in a natural relationship to the butt plate and pistol grip. The rear sight I9! is conveniently mounted on the block l6 before mentioned.

An oiler I08 received in a recess in the stock has a cap I99 provided with, bayonet type lugs which are capable of passing through the butt plate I I9 and turned into recesses in typical bay- .onet joint fashion. A washer and spring confined thereby around the oiler tend to hold the lugs in their locked position and prevent loss or rattling of the .oiler.

To summarize the operation of this. firearm it may be seen that a loaded magazine 16 may be inserted into the appropriate opening in the trigger housing until it is retained by engagement with the magazine latch M. The bolt may then be drawn rearwardly by the cooking handle 94 until the sear 53 engages the shoulder on the inertia'block 5. Release .of the cooking handle when the sear has engaged the bolt results in return of the cooking handle by the spring N13 to a position in which it is engaged andretained by the latch IM. This places the arm in readiness for firing and when the safety lever 81 has been turned to downward position the gun may be of the end of the bolt proper It will strip the top cartridge 21; from the magazine 16 and chamber it at I IS in the barrel 2, in the conventional manner. As the cartridge moves into the chamber, it becomes coaxial with the bolt, which will continue forwardly while the firing pin 1 drives into the primer of the cartridge and fires the round. The tendency of the cartridge to be blown rearwardly from the chamber becomes manifest and such movement with the sustained pressure of the propellant acting between thebullet and the cartridge'will absorb a part of the momentum of the bolt and block 6 as the cartridge case becomes fully chambered, and the completely chambered cartridge case will be pressed back within the rim l l l of the bolt and under the hook ll of the extractor while the recoil of the bolt .is begun. The delay in return of the spent cartridge permits the bullet to leave the barrel before the breech is opened, and residual pressure .of gases in the barrel continues the recoil and drives the cartridge and bolt to the rear, the

cartridge being 'held coaxially on the bolt until the rear face of the cartridge head engages the ejector 23, which swings the cartridge about the extractor claw and throws it out through the port 25.

If it be assumed that the selector 6? was set for full automatic fire as shown in Figure? the bolt will continue rearwardly until it is stopped by the action of the drive and buffer springs 22 and is. As the bolt returns forwardly the cycle above described will repeat itself until such time as the ammunition is exhausted from the magazine or the trigger is released to permit the sear 53 to reengage the bolt lug 52. The function of the cam hook 68 with the flat 68 of the selector, in automatic fire has been before explained herein.

When the selector, mechanism has been set for semi-automatic fire as shown in Figure 6 actuation of the trigger to initiate the firing cycle will result in the tripper '55 being drawn forwardly .(by engagement with the body of the selector) to a position in which the rear endof the tripper becomes .disengaged from the sear, permitting the sear to return to position in which it willreengage the bolt as the latter is driven rearwardly by the fired cartridge. It will be necessary to release the trigger and thus reengage the 'tripper with the toe .of the sear before another round canbe fired. In other respects the operation: is the same as for automatic fire.

When the trigger is released under thelast named conditions, the trigger spring 64 acting through the plunger 65 presses the tripper upward at its forward part, and this acting against the trigger pin 58 as a fulcrum and against the rear part of the trigger, rocks the trigger, the tripper moving likewise. The spring 62 while pressing against the seat lug 6| maintains the tip of the cam hook 69 against the cam fiat (-58 at the inner side of the notch in the shaft 6B of the selector so that as the cam hook rises it also moves toward the rear. The rear end of the tripper will first engage wipingly against the toe 56 of the sear, which will for a time delay rearward movement ofthe tripper, and when the end of the tripper passes below the toe of the searyit will be snapped to full rear position under the toe of the sear, ready for a repeated operation of the trigger in firing relation to the sear.

To disassemble the gun for routine inspection it is merely necessary to depress the catch 39 from the band 88 and slip the band longitudinally from the stock 34 and hand guard .35, after which the arm 42 of rotary lock 4| is swung'to the left side to release the trigger housin from the receiver. The barrel and receiver maythen be removed by swinging the muzzle of the bar'- rel through an are having its center at the lug 32 engaging the one 32 on the recoil' plate 33. In the event that any further disassembly of the receiver group is necessary this may be accomplished byturning the cap I4 out of engagement with the blocks 16 and IS on the bolt housing, permitting withdrawal of the bolt assembly with the cap. 5 The trigger housing group will not require further disassembly for any field operations since the whole trigger mechanism is exposed for inspection and cleaning when the receiver group has been removed. If it should be necessary to replace any parts the screws H4 holding the trigger housing in the stock are readily removed with a coin or other flat piece to expose the ends of the trigger and sear pivot pins which may be punched out with a drift pin, a match or other conveniently available member,

It will be seen that in this manner there has been produced a submachine gun which maybe used and maintained with facility, and which is capable of being manufactured economically in large scale production. I 1

It should be noted-that the sear 5-3 andthe auxiliary sear 8| are'soshaped and mounted that they completely close the slot H5 in the lower side of the housing 3, when the stock group is assembled to the barrel group (comprising the housing 3, receiver I! and barrel 2), and thereby when the bolt is allowed to remain in battery, the whole bolt assembly and receiver are Well closed against access of mud, dust, sand and other detritus. At the same time, as before explained, when the stock and the trigger frame are so assembled to the barrel group, the trigll ger assembly is completely enclosed, with like advantage. The pivot of the sear 53 is located directly under the forward end of the slot H5,

and the rear end of heel 52 of the sear is formed with an end face which is substantially concentric with the pivot of the sear, and so close to the rear end edge of the slot H in the housing 3, that no material ingress of dirt Will occur there, because this part of the sear extends into the housing 3 at all positions of the sear.

It will be apparent also, that by breaking of the barrel assembly from the stock by release of the collar 38 and pivotal movement of the barrel unit on the lug 32', an opening is efiected at the slot in the lower side of the housing 3 by lowering of the sear therefrom, at the same time that the trigger assembly is laid open. This makes it possible to quickly wash out the bolt assembly in case of need, using either water or oil, alternatively or successively, and a similar cleaning of the trigger assembly is at the same time made possible by the same procedures. In case the gun becomes filled with water by prolonged submergence, the bolt assembly may be quickly emptied by cocking the gun and allowing the water to drain out through the port 25.

The trigger frame and its operating parts present a highly effective let-off unit device, with manually operable safety changeable at will instantly, and with a readily changed manually operable selector device, also operable at any instant at will, without involving material disturbance of the sighting and firing of the gun.

Although the invention has been described and illustrated in considerable detail it will be realized that modifications may be made in the various elements without departing from the spirit of the invention as described in the claims appended hereto.

We claim: a

1. A firearm comprising a trigger, a tripper having a depending hook on one end thereof and mounted on the trigger for vertical and horizontal movement, a sear engaged with the tripper, and selector means in the path of vertical movement of the tripper with the trigger and in the path of horizontal movement of the tripper on the trigger adjustable to one position and shaped to cam the tripper along the path of its horizontal movement on the trigger to clear said i sear under movement of the trigger to a predetermined firing position after said sear has been actuated to firing position, and in another position to receive the tripper thereagainst in movement with the trigger, said selector means comprising a rotatable shaft on an axis transverse to the firearm and extendin substantially therethrough, and shaped at one side into a recess longitudinally of the said shaft forming a cam with shoulders on each side of the said recess, the said depending hook being positioned in said recess between the said shoulders at the said one position of said tripper and trigger and throughout the rocking and sliding movement of said tripper, said selector means movable at will to the said other position in an oppositely disposed position relative to the tripper to receive the said depending hook thereagainst and between the said shoulders to prevent the movement of the said tripper to clear the sear.

2. A firearm comprising a trigger, a sear adjacent thereto, a tripper slidable on the trigger arranged at one position to engage and move the sear and hold it on operation of the trigger, and selector means adjustable to and from a position in the path of the tripper and constructed and arranged to cam the tripper from the sear, said tripper having a depending hook at one end thereof in engagement with said selector means,

said trigger channelled in its top side longitudi-,.

nally and pivoted on a trigger pin, said sear being pivoted rearwardly of said trigger and clear thereof, said tripper being slidably fitted in said channel and havin a longitudinal slot transversely therethrough receiving said trigger pin, spring means urging the tripper to normal horizontal position in relation to the sear to engage the same whereby the tripper and trigger are held in operative relation to the sear, said tripper lying clear of the sear when at the forward limit of its horizontal movement on the trigger, said selector being a rotatable shaft on an axis transverse to the firearm and extending substantially therethrough, having its axis below the trigger pin and shaped at one side into a longitudinal recess to receive the said hook, the inner side of the recess being a smooth cam face which at one position lies behind and engages said cam hook and inclines across the path of the said cam book under firing movement of the trigger to slidably cam the said tripper clear of the sear,

and at an opposite position lies before the said cam hook for movement of the tripper without sliding movement.

FREDERICK W. SAMPSON. GEORGE J. HYDE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date GreatBritain June 13, 1913 Number Number

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