US2567198A - Receiver and bolt mechanism for firearms - Google Patents

Description

Sept. 11, 1951 J. c. GARAND RECEIVER AND BOLT MECHANISM FOR FIREARNIS Original Filed Sept. 26, 1945 .M1 @Emmen Patented Sept. 11, 1951 RECEIVER- AND BGLT MECHANISM FOR FIREARMS John C. Garand, Springfield,` Mass., assigner toy the United States of America as represented by the-Secretary of War Original application September 26, 1945, Serial' Divided and this application March 19, 1947, Serial No. 735,589-

(Granted under the act of March 3, 1883', as amended April 30, 1928;Y 370 0. G'. 757) Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to an improved bolt and receiver construction for automatic rearms.

This application is a division of my application Serial No. 618,805, led September 26, 1945 f'or Firearms, now Patent No. 2,505,760.

The usual receiver and bolt construction for automatic firearms is generally of complicated design and consequently is extremely diicult to.

machine to the exacting dimensions required. This is particularly true of the bolt camming surfaces and of the locking surfaces or shoulders within the receiver against which the locking lugs on the bolt cooperate to lock the bolt to the receiver prior to discharge of the cartridge.

Accordingly it is an object of this invention to provide a receiver and bolt of improved design thereby facilitating fabrication of' such receiver.

Another object of this invention is to provide a splined liner for a receiver terminating in a shoulder to provide a locking surface for the locking lugs for the `Firearm bolt.

Still another object of this invention is to provide a firearm bolt having cooperating lugs thereon adapted to engage the splined liner of the receiver.

A further object of this invention is to provide an improved means whereby the bolt is rotated to its battery position.

The specific nature of the invention as well as.

other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. l is a longitudinal sectional view of the rearms;

Fig. 2 is a side elevational view of the receiver;

Fig. 3 is a cross sectional View taken along the line 3 3 of Fig. 2;

Fig. 4 is a side elevational View of a firearm bolt;

Fig. 5 is a view similar to Fig. l but showing the bolt rotated 90 degrees;

Fig. 6 is a rear end view ofthe bolt shown in Figs. 4 and 5;

Fig. 7 is a side elevational Viewl of the liner; and

Figure 8 is a side elevation of the splined end of the bolt, rotated approximately 72 clockwise from the position shown upon Figure 6.

The receiver assembly I comprises essentially a receiver 9, a magazine latch 30, a magazine latch 2. spring 32, a liner 43, a rear sight 50 mounted on top of receiver 9, an ejector 62, a cap 61 and a buffer disk l2.

The receiver 9, Fig. l, is in the form of a generally cylindrical hollow member defining an axial bolt-way I D' and is provided with two downwardly depending lugs, a forward lug Il, and a rearward lug. I2 through which. are provided coaxial holes I3 and I4 respectively, parallel to the axis of bolt-way IU for a purpose to appear later. ln rear l'ug I2 is a counterbored threaded hole l5 extending obliquely upward, radial to bolt-way I D, from theleft side.

An ejection slot Il leads from bolt-way I9 downwardly toward the left between lugs II and I2. A magazine well I9 is provided in receiver. 9 leading from bolt-way IU upwardly toward the right, substantially opposite ejection slot I'I, the receiver being extended. aroundy well I9 to form a wall 2li. A crosswise undercut. 2| is provided at the forward end of, magazine well I9 and a longitudinal slot 23 is provided ina rearward portion 22 of wall 2li. A magazine latch 30 is piv otally secured. in sl'ot 2.3 by a transversely located pin 3 I Five inwardly projecting splines 38,` preferably of' equal Width, are provided in the rearward half of bolt-way I9 in receiver 9; similar tothe construction described in my prior Patent 2,386,205 for Firearms.

These splines, as will be shown later are provided for cooperation with bolt Ill, being rounded at the front corner for that purpose as shown at 39, and are equally spaced around the inside of the receiver 9. A slot 4| is provided extending through the wall' of' the receiver in alignment with holes. i3 and Il! in lugs Il and l2 and extending from the rear end of receiver 9 forward and opening into hole Ill. This slot occupies the space between two of the splines, the widthk of slot il corresponding to the width ofthe space between the splines. A small notch 42 is provided in one side of slot @I for a purpose to appear later;

A camming shoulder 44a is required in bolt-way l0 forwardV of: splines 38 and facing rearward', that is, toward the splines to initiate the rotatiner of the bolt relative to the. splines. In order to obviate the. diiculty of machiningr such a cam surface in the receiver, a tubular liner. 43 with the rear end formed to constitute shoulders 44u. and Mb (Fig. '7) is provided for assembly within receiver 9, being suitably secured in fixed location therein by means of a set screw 45 through counterbored obliquely disposed threaded hole I6.

Shoulder 44a is rounded and is arranged to provide a camming action to bolt in a manner to appear later. Shoulder Mb is square and serves as a supplementary stop to prevent excessive rotation of bolt |00 as will be shown later. Liner 43 is cut away as at 46 to match ejector slot and as at 4l to match magazine well I9. In the assembled relation, edges 48 of magazine wellcut 4l in liner 45 serve as shoulders against which the magazine (not shown) is held for positioning.

The use of a liner for obtaining a camming shoulder within the bolt-way in the receiver, without involving the diiiiculties of making an interior radial shaving cut, provides obvious advantages in simplicity of manufacture.

A thread 66 is provided-on the rear end of receiver 9 for assembling a cap 61. This cap is provided for holding a buffer disk 'l2 in loc-ation at the rear end of bolt-way |0 to serve as a stop for cushioning the recoil stroke of the bolt |00. On one side of cap 0l adjacent the open end is provided an oblique lug 68 and extending through such lug is a rounded, radially disposed slot 0S as shown in Fig. 1. A radial key-way 1| is provided across the forward face of lug 58 on cap 6l, coinciding with the center of slot 69.

The barrel assembly 2 comprises a barrel 80 having threads 8| for assembling to receiver 9, a chamber 82, and a bore 83. Chamber 82 accommodates a cartridge 8 having a case 16. An enlarged front end bearing portion 84 is provided to serve as a bearing for a front sight 8l comprising a sleeve 88 and a vane 89, the Vane being offset to the left with respect to the axis of barrel 80 in order to align with a rear sight 50. Sleeve 88 is assembled on bearing 84 and .is secured in location by a dowel pin 90 provided for that purpose.

A second bearing portion 85 with a radial gas port 86 through the bottom thereof is provided somewhat to the rear of bearing 04. A sleeve member 95, integral with a gas piston 96, is mounted on bearing 85. An aperture 91, in alignment with gas port 86 extends from inside of gas piston sleeve 95 radially outwardly, thereby providing a continuous passage from the bore 83 of barrel 80 through gas piston 96.

The bolt assembly 3 consists of a bolt |00, an extractor 8, a firing pin |35, and a firing pin spring |40.

Bolt |00 is of generally cylindrical form and is provided with an axial ring pin aperture |0|, terminating at its forward end in a ring pin orifice |02. The juncture of ring pin aperture |0| and ring pin orice |02 constitutes a shoulder |03.

In the rearward portion of bolt |00 is a longitudinal slot |05 extending inwardly to intersect firing pin aperture |0|. The rear portion of slot |05 is extended obliquely rearward to the right as at |05 forming at the rear an oblique cam surface |01 and at the forward end of slot extension |06 a cam surface |08. A left wall ||2 of slot extension |05 serves as a stop as will be shown. A slight shoulder |09 is provided in cam surface |08, all for cooperation with other parts as will be shown. A radial vent hole ||0 is provided through the wall of bolt |00, just rearward of shoulder |03 to permit escape of any gases passing through the `ilring pin orifice |02 as a result of a punctured primer.

In the forward end of bolt |00 is a circular recess coaxial with firing pin orifice 02 for receiving the head of a cartridge 8 when in lll engagement therewith. An extractor I8 is provided along one side of bolt |00.

Diametrically opposite extractor ||8 in bolt |00 is an ejector clearance groove |25. This groove extends from the front end of bolt |00 rearward to about the middle of the bolt at which point it is extended sidewise to the left as at extension |26. This ejector clearance groove and extension |26 provide clearance for ejector B2 when the bolt moves forward and rotates into the locked position.

On the rearward portion of bolt |00, five lugs |a, |300, |30c, |30d and |306 are provided for cooperation with splines 38 in receiver 9 in a manner similar to that described in my above referred to Patent No. 2,386,205 for Firearms. However, in accordance with this invention, lugs |30@ and |3019 are longer than the others, lug |30a being rounded at its forward end as at 3| and arranged to engage camming shoulder 40a on liner 43 in receiver 9 and thereby initiate rotation of bolt |00 toward the locked position as it reaches the end of the forward stroke. If, as a result of wear or for any other reason lbolt |00 fails to stop its rotation in proper locking position, shoulder 44h is provided to serve as a supplementary stop by eng-aging lug |30b at the appropriate position. The rear corners |32 of bolt lugs |30 are rounded for a purpose to appear later.

A firing pin |35 of substantially cylindrical form is slidably contained within bolt |00 as shown in Fig. 1.

The operating rod unit 4 consists of an operating rod |45, a set screw |50, an actuator |52, an actuator spring |59, and a spring guide |60.

Operating rod |45 is expanded at the forward end to form a cup or gas cylinder |40. The rearward end of the operating rod comprises a socket |41 and an operating arm |48.

Actuator |52 is of generally cylindrical form and has an axially aligned cylindrical stud |53 at the forward end arranged for engagement in socket |41 of the operating rod |45, being secured therein by set screw |50. Actuator |52 is substantially hollow, an axially coincident hole |54 extending through the actuator from the rear end to a point near the forward end, actuator spring |59 being inserted in such hole. A lugr |55 provided on the upper rear end of actuator 52 is arranged to be engaged in slot |05 and slot extension |05 in bolt |00, whereby the motion of actuator |52 is transmitted to bolt |00 as will be shown later. A shoulder |56, with a forwardly facing bevel |57, is provided on the underside of actuator |52 at the rear end thereof, the purpose of which will appear later. Flutes (not shown) are provided in actuator |52 for lightening purposes.

The actuator spring guide |60 in the form of a tubular member is surrounded by actuator spring |59. This guide has a collar |6| at its rear end and a radial lug |62, the collar |6| serving as a shoulder for engaging the rear end of actuator spring |59.

In assembly, actuator |52 is slidably contained within aligned holes |3 and I4 in lugs and |2 respectively on receiver 9. Lug on actuator |52 extends generally upward through slot 4| in receiver 9 and into slot |05 in bolt |00. By this means longitudinal motion of actuator |52 is transmitted to bolt 00. Operating rod |45 is as- Sembled to axial stud |53 of actuator 52, gas 4cylinder |45 on its forward end slidably engaging 55S piston 96 on barrel 80. Cap 61 is threadably acordes assembled with buffer disk 7?; therein at` the end of bolt-way- I) to the rear end of receiver El,y and with slot @il in. lug" 53" in; axial alignment with. hole |54 in. actuator |52. Actuator spring guide |50 isinserted in the rear; end of. actuator' spring |59', the forward end of such' springt being, passed forwardly throughlslot fln lug 53 into hole` |55V in actuator |52.

Guide |05 is now-"forced:v forwardlyJ compressing spring |59l anclte'lescopin-g into actuator* |1521y until lug |524 on guide' |50 passesthroughr slot 591m lug 682 on cap 5:?. The. guide' is then rotated until lug |02 thereon has passed through notch i1-2 in receiver slot it andA comes into aligrnnent-` with radial key-way 1| in capdug BS whereupon guide |50 is allowed toretractseating zlug; |62on spring guide,v |60 in keyvvay' 'H-4 in lug 55 of capY 0-1. In this position actuator spring.' |59- is` under considerable'. compression thcreby maintaining actuator ifZ under a posit-ite forweordV stress at all times.

A. trigger' mechanism 5 consisting essentially of a trigger guard ieri hai-ing a trigger slot it-a trigger having a seal' stop |210-, a pawlI |82; a safety 595, a sear 53 having a beveledshoulder 203; asear spring 2&0, a plunger 2M and plunger spring 220 is provided' to control theiire of the iirearm.Y Assuch mechanism constitutes noipart of this invention no further mention thereof will. beL made except asl to describe the' function thereof in cooperation* with the actuator. Such trigger mechanismsismounted on theunderside of receiver Gas shownfin Fig. 1,.

The above described; firearm is of the'gas-operated type, the gas'being taken from the bore 83 of. barrel 80 through gas port 3.5e into" gas cylinder Iddon' thel end of operatingI rod |55.; the gas pressure developedy in the gas cylinder upon. dischar-ge oi? cartridge forcing the operating rod |45 and` the actuator |55 rearwardly.. Lug, |55 onr the topic-i1 actuator i52-l being engaged in. slot |05vinV bolt |50 ino-ves rearwar ly and engages rearward canin-ring1 surface. |01.. in; the. bolt slot |85-, thereby imparti-ng an: oblique thrust against the bolt.tll1efthr.ust bei-ng rearwmd and counter clockwise-.s 'The lugs. i3dA on boltl |00 being in endwise engagement with, splines 38 in the receiver 9- prevent rearward motion of the bolt. Bolt i0@ being free to respond only to the counterclockwise rotary component of the force is therefor rotated in a counterclockwise direction until the lugs i235 on the bolt pass'out ci endwise engagement with splines 38 in the receiver. Lug |55 then engages the left wall H2 of slot extenn sion |05, thereby stopping rotation of bolt |795 with splinesiand lugs inslidable relation and hence-converting the motion et bolt liilrfromithe counterclockwise rotary movement to axrearwar'd longitudinal movement. The rounding at 3e and |32 on splines 58 andv lugs |30 respectively provides clearance for facilitating the above describeditranslation of motionzoi' bolt |55;

Bolt |00 now moves rearwardly; extractor' H5 holding: the cartridge case 'I-'f engagement in recess in the head of the bolt and thereby withdrawing the case from chamber 82 of barrel 80. As the case 16 is moved rearward, it is engaged near the edge opposite extractor H8 by the ejector 52 and is thereby ejected through slot I1. Meanwhile bolt |00 has passed to the rear of magazine well I9 in receiver 9 allowing the lowest cartridge t in magazine (not shown) to be moved by the magazine follower (not shown) to the bottom position where it is engaged by the edge of bolt |00 on its return stroke 6. and c-arriedforward into the -chambenso bar,-

reit);y

Asfactuator |52; moves rearwardly, actuator spring |59: is subjected toadditional compression; hence at the endY of the rearward stroke spring |55V is; under maximum compression. Therefore theV full compressive force of the spring is eX- erted forwardlyagainst.actuator |52. Thiszforce causes; the actuator: to immediately return forwardly, lug |55 engaging shoulder l 05 on forward c'amming surface |08`inbolt |00 andsplines38 and" lugs |35 being in. sidewise" engagement, the bolt cannot rotate but instead: moves forward until the; splines and lugs are'disengaged andthe rounded shoulder |3`| on lug |3011` on bolt |00v engages. camming should. 44a in liner i3 thereby camming; the boltin aI clockwise directionito dis,- engage lug |v fromzshoulder |09 onto cammina surface |08 which thereby rotates the: bolt into the fully lo cked'position.

At this point bevel |51" on shoulder |50 on actuator |52V engages-beveled shoulder 203v on seal |08, cammingv the sear downward, but sear stop |15; on trigger |15 engages the sear just'y to the rear Iof trigger slot |59 thereby preventing fur'- ther downward motion and. retaining shoulder 2-03 there-on in engagement. with shoulder |55 on the actuator so that actuator |52 is stopped immediately after boltV |00 is locked in ring position. but whileA 'the bolt is still about one-halfv inc-h from thefextremeforward position.

When trigger |111 is pulled back, sear: stop- H6 onthe trigger is pivoted forward out ofi engagement with sear |98 into alignment, with trigger slot HB9 thereby permitting the Sear to*V move downward under the camming force of. actuator |52, which, being freed from engagement by the sear,f.moves forward; under' the thrust of actuator spring. |55` Lug |551" on the actuator engages firing pin v|35 driving it forward to strike the cartridge.

As soonas the cartridge is red, the gas press sure developed tends -to force the cartridge case and bolt |00 rearwardly, but splines 38 inthe receiver 5l and lugs |30 on bolt liiilbeingV in end.- wise engagement, the bolt is thereby prevented from moving rearwardly. As soon as the-bullet. of cartridge 8- has passed gas port 80 in thebarrel 80, gas escapes. through the port 35' and. aperture 91 into gas cylinder |45 on operating rod |55?v driving the entire operatingv rod assembly rearward to! repeat. izlracyclev above described.

From-'the foregoing description it is readily apparent' to those skilled' i'n the artthat therev is here provided an improved' firearm receiver and bolt wherebyvrt difficult and expensive machining operations' areV substantially eliminated resulting in greatly-increased production and large savings irl-costs.

I claim:

1.`I`n a firearm, 'the improvement comprising; ahollow receiver having ja bolt-way therethrough, a cam shoulder within said bolt-way, said shoulder being generally 'helically disposed with respect to the axis of the bolt-way, a bolt reciprocably mounted in said bolt-way and having a rotated locked position at the forward end of its reciprocating motion, a projection on the bolt constructed and arranged to engage the cam shoulder at the forward end of the bolts reciprocating motion, whereby the bolt is rotatably cammed toward its locked position, said bolt having a laterally disposed recess, said recess having a cam wall generally helical with respect to the axis of the bolt, an actuator slidably mounted assignee in the i'lrearm, and a lug on said actuator endisposed with respect to the axis of the ibolt-way,

a bolt reciprocably mounted Within said bolt-way and having a rotated locked position at the forward end of its reciprocating motion, a plurality of circumferentially spaced external lugs on said bolt, said bolt lugs slidably cooperating with said receiver splines to maintain the bolt in fixed angular alignment in the receiver during its reciprocating motion, said bolt lugs and said receiver splines being constructed and arranged so that said bolt lugs pass out of sidewise engagement with said receiver splines at the forward end of the reciprocating motion, and a projection on said bolt, said projection :being constructed and arranged to engage the cam shoulder in the boltway as said bolt lugs and receiver splines pass out of sidewise engagement to thereby initiate rotation of said bolt into locked position.

3. In a rearm, the improvment comprising, a receiver having a bolt-way therethrough, a plurality of circumferentially spaced internal splines in said bolt-way, a cam shoulder within said -boltway, said shoulder being generally helically disposed with respect to the axis of the bolt-way, a bolt reciprocably mounted within said boltway and having a rotated locked lposition at the forward end of its reciprocating motion, and a plurality of circumferentially spaced external lugs on said bolt, said bolt lugs slidably cooperating with said receiver splines to maintain said bolt in xed angular aligmnent in the receiver during its reciprocating motion, said bolt lugs and said receiver splines being constructed and arranged so that said bolt lugs pass out of sidewise engagement with said receiver splines at the forward end of the reciprocating motion of the bolt, one of said bolt lugs being constructed and arranged to engage the cam shoulder in the bolt-Way to initiate rotation of said bolt into locked position at the forward end of the reciprocating motion of said bolt.

4. In a firearm, the improvement comprising, a receiver, a liner secured in coaxial relation within said receiver, said receiver and said liner together defining a bolt-Way extending longitudinally therethrough, a cam shoulder formed on the rearward end of the liner, said cam shoul-Y der being generally helically disposed with respect to the axis of the bolt-way, a plurality of circumferentially spaced internal splines in the bolt-way `in the receiver, a bolt reciprocably mounted in the bolt-way and having a rotated locked position at the forward end of its reciprocating motion, and a plurality of circumferentially spaced external lugs on said bolt, said bolt lugs slidably cooperating with said receiver splines to maintain the bolt in xed angular alignment in the bolt-way during all but the extreme forward portion of its reciprocating motion, said bolt lugs being longitudinally disposed relative to said receiver splines so that at the forward end of the reciprocating movement of said rbolt, said lugs pass out of sidewise engagement with said receiver splines, one of said bolt lugs -being constructed and arranged to engage the cam shoulder on the liner to initiate rotation of said bolt toward locked position at the forward end of its reciprocating motion.

5. In a rearm, the improvement comprising, a receiver, a liner secured in coaxial relation within said receiver, said receiver and said liner together dening a bolt-Way extending longitudinally therethrough, a cam shoulder on the rear- Ward end of the liner, said cam shoulder being generally helically disposed with respect to the axis of the bolt-way, a plurality of circumferentially spaced internal splines in the bolt-way in the receiver, a bolt reciprocably mounted in the bolt-Way and having a rotated locked position at the forward end of its reciprocating motion, a plurality of circumierentially spaced external lugs on said bolt, said bolt lugs slidably cooperating with said receiver splines to maintain said bolt in fixed angular alignment in the bolt-way during all but the extreme forward lportion of its reciprocating motion, said bolt lugs and said receiver splines being constructed and arranged so that said bolt lugs pass out of sidewise engagement with said receiver splines at the forward end of the reciprocating motion of said bolt, one of said bolt lugs being constructed and arranged to engage the cam shoulder on the liner to initiate rotation of said bolt into locked position at the forward end of the reciprocating motion of the bolt, said bolt having a laterally disposed recess, said recess having a cam wall generally helically disposed with respect to the axis of said bolt, an actuator slidably mounted in the firearm, and a lug on said actuator engaged in said recess in said bolt, said lug cooperating with said cam wall to complete the rotary motion of said bolt to its locked position.

JOHN C. GARAND.

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

UNITED STATES PATENTS Number Name Date 1,132,044 Stamm Mar. 16, 1915 1,925,776 Scotti et al Sept. 5, 1933 2,386,205 Garand Oct. 9, 1945 FOREIGN PATENTS Number Country Date 151,781 Germany June 17, 1904 212,840 Germany Aug. 11, 1909 213,930 Switzerland June 16, 1941

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