US2539644A - Tilting breech bolt lock actuating mechanism - Google Patents

Description

Ian. 30, 1951 R. J. TURNER TILTING BREECH BOLT LOCK ACTUATING MECHANISM 2 Sheets-Sheet 1 Original Fild Jan. 3, 1942 E WM RN MN Jan. 30, 1951 V J. TURNER TILTING BREECH BOLT LOCK ACTUATING mscx-mmsm 2 Sheets-Sheet 2 Original Filed Jan. 5, 1942' Patented Jan. 30, 1951 TILTING BREECH BOLT LOCK ACTUATING MECHANISM Russell J. Turner, Butler, Pa. Original application January 3, 1942, Serial No. 7 425,541. Divided and this application June 15,

1944, Serial No. 540,404

16 Claims.

This invention relates generally to firearms and more particularly to breech loading gas-operated automatic firearms.

This is a division of the application on which United States Letters Patent No. 2,365,142 was granted on December 12, 1944, for Firearms.

This invention may be conveniently applied to all types of full and semi-automatic firearms such as machine guns, heavy rifles, light carbines, automatic pistols and other similar self or automatic loading weapons.

The principal object of this invention is the provision of an accurate and rugged. automatic, firearm the structure of which is reduced to a very few number of parts making the firearm simple in construction and in operation and economical to manufacture.

Another object is the provision of an automatic firearm that may be completely dismantled without the use of hand tools.

Another object is the provision of a breech loading gas-operated automatic firearm that employs the gas pressure of the charge to unlock, withdraw and open the breech, cock the piece, xtract and eject the shells, insert a fresh load from the magazine, lock the breech and fire the load.

' Another object the provision of a double stepped triggerthat converts the full automatic firearm into a semi-automatic firearm which requires the trigger to be pulled to fire each shot.

' Another object is the provision of an operating arm having a cam surface which locks the breechblock in its firing position and when initially retracted by gas pressure unlocks the breechblock by withdrawing the cam surface from its operating position.

Another object is the provision of a novel link which connects the operating .arm with the breechblock and serves to dislodge the breechblock from its seat and slide it rearward1y to open the breech, cock the piece, and extract and eject the empty shell.

i Another object is the provision of a'novel firing pin and an extension on the breechblock connecting-link which prevents the firing pin from engaging the primer unless the breechblock'is fully locked in its closed position. V

Another object is the provision of a shoulder in -t-he side of the receiver against which the breechblock maybe seated and locked in "its closed position:-

Another object is the which is tightly closed when the breechblock is, locked-in the firing position and is opened in-v stantaneously when the empty shell is ejected through an opening in the operating arm when in its retracted position.

Other objects and advantages appear in the following description and claims.

In the accompanying drawings a light semiautomatic carbine is employed as a practical embodiment to illustrate the principles of this in-. vention wherein:

Fig. 1 is a top plan view of the firearm with parts in section and parts broken away, showing the breechblock inits retracted position.

Fig. 2 is a view similar to Fig. 1 showing the breechblock in its closed and fully locked position.

Fig. 3 is an enlarged transverse sectional view illustrating the breechblock and operating link in the position shown in Fig. 2 with parts broken away.

Fig. 4 is a side elevation of the operating arm and the breechblock with parts in section and parts broken away. 7 r

Fig. .5 is a top planview of the firing pin in the firing position with the link illustrated in dotted lines.

Fig. 6 is a view similar to Fig. 5 illustrating the firing pin locked in its retracted position.

Fig. 7 is a perspective view of the under side of the link. 7

Fig. 8 is a side elevation of the hammer and trigger mechanism with parts broken away, illus trating the semi-automatic feature.

Fig. 9 is an enlarged view of a modified firing pm.

Fig. 10 is an enlarged view of the firing chamher with the breechblock partially retracted from its firing position.

Referring to the drawings the body of the firearm comprises three parts, the barrel 10, the receiver or frame II and the grip or stock I2. The breech end l3 of the barrel is fitted to the front end of the receiver II and projects into the forward end of the receiver chamber 14. The stock i2 is secured to the rear end of the receiver or frame I I. The forward end of the receiver chamber I4 is open at the bottom to admit the cartridge magazine l5. The right side of the receiver is provided with opposed grooves It in a. longiprovision of a receiver tudinally extending slot which extends for the full length thereof and which slidably carry the action or operating arm ll. On the same side the rear portion of the receiver chamber I is closed by a removable cover plate 18 which retains theoperating arm l1 and covers the hammer 20 and the trigger mechanism 2|. By first 3 removing this cover plate the whole firearm may be dismantled.

The breechblock 22 is arranged to slide longitudinally Within the receiver chamber l4 and carries the firing pin 23. The front end of the breechblock is recessed in the usual manner as indicated at 24 to receive the rim and primer of the cartridge shell 25. The extractor claw 26 is pivoted in the side of the breechblock and extends forwardly and inwardly to catch on the rim of the cartridge to extract it from the breech of the barrel. An ejector 2? is fixed to the Wall of the chamber l4 and is arranged to strike the rim of the cartridge shell and swing it toward the extractor claw when the breechblock is substantially fully retracted. An aperture 28 is provided in the forward portion of the operating arm H to permit the shell to be thrown out of the receiver chamber when the operating arm is in its retracted position.

In the left side at the front of the receiver chamber a pocket is provided which tapers towards the breech from the beveled shoulder 3|. The corresponding side of the back of the breechblock is provided with the beveled surface 32 which is complementary to and is received by the shoulder 35. When the breechblock is brought forward until the front end engages the end of the barrel it is then shoved sideways to seat the surface 32 on the shoulder 3|. The front end of the breechblock is at this time normal to the axis of the barrel and held tightly thereagainst.

The breechblock is shoved sideways into the pocket 3% by means of the complementary cam surfaces 33 and 34 at the rear ends of the operating arm I 7 and the breechblock 22 respectively. The operating arm is permitted more travel forward than the breechblock. When these two members are retracted to the rear of the receiver chamber 54 the cam surfaces 33 and 34 intermesh as illustrated in Figs. 1 and and the forward travel of the operating arm moves the breechblock forwardly through these cam surfaces until the front end of the breechblock engages the end of the barrel. The breechblock is stopped but the operating arm continues to move forwardly and the cam surface 33 rides up the cam surface 34 and shoves the rear end of the breechblock to the left into the pocket 35. The breechblock is of such length that the beveled surface 32 seats firmly on the shoulder 3i and is locked in place by the cam surface 33 resting on the outermost surface of the cam 34.

The complementary surfaces 3| and 32 are beveled to such a degree that the blowback of the recoil would unseat and force the breechblock to the back of the receiver chamber I 4 if it were not for the fact that the cam 33 locks the breechblock in its seated position.

The operating arm and the breechblock are operatively connected by the link 35 which is provided with a depending stub shaft at each end thereof. The stub shaft 35 is journaled in a vertical opening in the rear end of the operating arm and the stub shaft 3? is journaled in the vertical opening 39 which extends into the firing pin chamber of the breechblock. The curved portion of the cam surfaces 33 and 34 are arcs struck from the axis of the stub shaft 31 which eliminates any interference between the action of the cam surfaces and the action of the link. There is no play or clearance permitted between the link and its associated parts. Thus the operation of the cam surfaces and the link are in phase which produces a smooth and uniform action.

A portion of the outer end of the stub shaft 3'! is cut away, leaving the vertical cam face 38 which lies in a plane passing through the axes of the stub shafts 3.5 and 37. The end of the shaft 31 carrying the face 38 extends within the firing pin bore and is received in the slot 40 cut in the upper surface of the firing pin 23. If the firing pin is large enough in diameter a circular groove 40 may be employed in place of the slot 40 which would permit the firing pin 23 to rotate as shown in Fig. 9. In the structure illustrated in Figs. 3 and 6 the firing pin is prevented from r0- tating because the end of the stub shaft 37 contacts or lies closely adjacent the bottom of the slot 45.

When the breechblock is seated and locked in the firing position as shown in Fig. 2 the longitudinal axis of the link 35 and the cam face 38 is disposed parallel to the transverse shoulder 4| in the firing pin forming the back of the slot 40. In this position the shoulder 4| is spaced approximately five hundredths of an inch from the face 38 as illustrated in Fig. 5. This clearance provides ample movement for the firing pin to discharge the primer of the cartridge for such movement may be five hundredths of an inch or less. If the link 35 is swung through a few degrees the cam face 38 engages the shoulder 4| to retract the firing pin 23 and prevent any forward movement thereof. Thus accidental striking of the firing pin by the hammer 20, or any other unforeseen object, prevents the firing pin from engaging the primer unless the breechlock is fully locked in its firing position with the link 35 positioned at right angles to the axis of the gun. It will be noted from the enlarged view of Fig. 5 that it takes very little swinging movement of the link 35 before the cam face 38 on the shaft 31 engages the shoulder 4| of the firing pin. This firing pin safety thus becomes effective before the breechblock is unlocked from its firing position.

The firearm used for the purpose of illustrating this invention is of the semi-automatic type wherein the trigger mechanism is provided with an upwardly extending fork member 43 having opposed shoulders 44 and 45 on the inner edges of the fork members. When the piece is being cocked by the breechblock sldiing rearwardly the hammer tongue 46, which is provided with the shoulders 4'! and 48 complementary to the shoulders 44 and 45, is inserted between the forked members of the trigger, permitting the shoulder 41 on the tongue to engage under the shoulder 4.4 of the trigger befor the latter has been released after the first firing. As the trigger is released the shoulder 44 slides off the shoulder 4'! and the shoulder 45 engages the shoulder 4a on the hammer tongue. When the trigger is pulled the shoulder 45 slides off the shoulder 48 and releases the hammer so that it is free to strike the firing pin 23. Before the trigger can be released the shell is fired and ejected and the hammer is recocked with the shoulder 41 again engaging on the shoulder 44. If the hammer shoulder 4'! did not engage the trigger shoulder 44 while the trigger was still held back the firearm would con,- tinue to shoot automatically.

Suitable safety means 50 are provided to lock the trigger mechanism 2|.

The fore end of the operating arm I! is provided with a knob 5| which may be grasped by the hand to retract the operating arm. Upon,

up a shell from the magazine 15 and inserts it into the breech of the barrel. The piece is thus cocked loaded and ready to fire.

An actuating rod 52 is detachably connected at one end to the fore part of the operating arm ii and at its other end to the gas piston head 53 which is arranged to operate within the gas cylinder 54. The rod 52 and the operating arm I! are normally retained in the forward position by the actuator spring 55 which is inserted under initial compression between the piston head 53 and the actuator bracket 56. The latter is secured to the barrel and is provided with a slot for receiving the actuator rod 52.

The fore end of the gas cylinder 54 is provided with the enlarged head 51, the peripheral surface of which is spherically ground to fit the spherically ground socket 58 in the gas cylinder block or support '60 that is secured to theside of the barrel adjacent the outer end.

In operation when the gun is closed and empty, and a full magazine hasbeen inserted, the breechblock 22 is pulled all the way back by the knob 5| on the operating arm H, which action cooks the piece. The knob is then released and the actuator spring 55 moves the breechblock forward, picking up a round from the magazine and inserting into the breech. Continued movement of the operating arm then locks the breechblock in place. When the cartridge is fired the bullet travels down the barrel l and after it passes the gas vent 64 a portion of the propellant gas blows back through the vent, filling the gas cylinder space and driving the piston 53, the operating arm and the breechblock back to the end of their stroke. The initial movement of the operating arm causes the two opposing cam surfaces 33 and 34 on the arm and breechblock to slide relative to one another to unlock the breechblock. When the operating arm I! starts to the rear the link 35 is swung clockwise, causing the face 38 on the shaft 31 of the link to engage the shoulder 4! in the end of the slot 40 in the firing pin 23. The swinging of the link' draws the firing pin back from the forward end of the breechblock and locks the same against forward movement. Any accidental breakage of the trigger mechanism causing the hammer to fall at the wron time could not fire the gun. Thus the initial rearward movement of the operating arm swings the link 35 which looks the firing pin and simultaneously slides the cam surface 33 rearwardly of the cam surface 34 until they intermesh as shown in Fig. 1 at which time the breechblock is completely unlocked. The cam surfaces 33 and 34 thus unlock the breechblock independently of the link 35.

If a round has been fired the breech pressure a will force the unlocked breechblock off the shoulder 3! and out of the pocket 3|]. The force of the breech pressure on the breechblock acts through the cam surfaces 34 and 33 to aid the force, previously transmitted to the operating arm, in moving the mechanism to the rear of the chamber. The link 35 takes no part in the action of these forces other than to maintain the cam surfaces in contact during the complete operation.

If the breech is opened manually by drawing back the operating arm by means of the knob 5|, then the link 35 gradually withdraws the rear end of the breechblock from the pocket 30 and off the shoulder 3| as the cam surfaces 33 and 34 slide over one another andthe' breechblock is completely withdrawn from the pocket when these cam surfaces intermesh as shown in Fig. 1. Further retraction of the operating arm draws the breechblock to the rear of the chamber. Under these conditions the link not only functions to lock the firing pin but it also acts as a coupling to pull the breechblock out and back. When the knob 5| is released the spring drives the operating arm forward. The cam surface 33 forces the breechblock forward, seats it and looks it by riding over the cam surface 34. The link 35 is not employed to transmit force to the block during this forward movement. 4

During the rearward stroke of the breechblockthe empty shell is carried back by the extractor claw 26 until the rim of the shell hits the ejector. 21 which throws the shell through the operating arm aperture 23 and out of the gun. As the breechblock draws away from the breech the extractor claw withdraws the empty shell and carries it back until the rim strikes the ejector, pivoting the shell on the extractor claw and swingtially fully retracted. During the rearward stroke the breechblock forces the hammer down, cans-- ing the shoulder 41 to engage under the shoulder 44 before the operator has a chance to release the trigger. The breechblock then strikes the rear Wall of the receiver chamber with the operating arm. The actuator spring 55 is then fully compressed and the stored energy then moves the mechanism forward. Upon its forward movement the breechblock picks up another round from the magazine and inserts it into the breech. When the breechblock is stopped in its forward travel by the barrel ID the continued pull of the actuator spring 55 on the operating arm causes the link to rotate counterclockwise and the two cam surfaces 33 and 34 slide upon one another, thus driving the end of the breechblock sideways into the pocket 30 and looking it on the seat 3|.

' When the operating arm ii is in the forward quick access to the hammer and position the aperture 23, through which the discharged shell is thrown, is forward of the receiver and any opening into the receiver chamber is closed against mud or sand or foreign matter that would ordinarily fall into the mechanism. The time that the aperture 28 is open during discharge is very short and the shell is on its way out during most of this time. Thus the firearm is very well protected and will continue to fire after being completely buried in mud. The cover plate l8 over the rear end of the receiver and back of which the operating arm ll slides provides trigger mechanism.

I claim:

1. In a'firearm, the combination of a barrel, a receiver secured to the barrel and provided with a, chamber, a breech block member mounted in the chamber for longitudinal reciprocation therethe pocket and which ride .upon Lone vanother tw move' the rear end oftthei'breechablock imember away lfrom theoperating :armandeinto seating engagement aagai-nstjatheishoulderlinithe pocket whenthe I frontzendr of'ithe breech -;block.' .mem-

ber-is inengagement with the front'a'wall; of '..;the chamber.

2. fm =a. firearmf the combination of :a receiver,

a breech-block member and adspringebiased operating arm'-'-memberreciprocallycarried w.IoyltheJreceiver, a pocket in the receiver,eashoulder eat the'rear'end of the pocket facingeforwardlyaand outwardly to-form:a seat;oontinuonslyeengaging and mating complementaryi overlappedzcamasurfaces of 1 reversed curvature; onizsai'dsmemberezinterengaged in; surfacelicontact to :transmitiblow back forces and :permit the springebiasedi. operating ar-m to move-:the' breechebeockito thei front or the receiver and -then slide oversoneaanother to seat and lock the breechblocki .memberain the firing-positionin said po'cketgandz meansrtmactuateusaid-operating arm'c m'ember.

3." Ina firearm; the combinationtof -a receiver,

"a breech-block member i, and -an operating arm member reciprocally carried by I the 1 receiver, :.a pocket in thereceiver; a shoulder at the rearen'd of the pocket facing forwardlyand-outwardlyzto form" a seat,- continuously engaginge and .mating 'complementary cam surfaces :onesaid em'embers having reversed circular -arc .portions interengagedin surface-contact to transmit blow back 'forces and' move the .breech-b1ock to the front 'of" the receiver and' thenslide overione another to seat arid lock the breechfiblock @member .in the-firingposition in-said polzketaan'd a link :hav-

ing spaced stub shafts -pivotally -conn-ecting said members permitting limited-relative zmovem'ent therebetween, said link pivoting on: the centers from which-the cam surfaces are-generated.

=-4.- In a fi-rearm,- the combination of -a receiver,

: a"-breechb1ock rmember andan'operating arm member reciprocally :carried by the receiven- -a firing pin carriedmy the breech blockmembema pocket-in the receiver-,= a shoulder-iatthe rearwend 'of the' po'cket facing forward-ly and outwardlywto I 'fo'rm a seat; continuously 'engagingzand:imating complementary: camasurfaces eon-maid :members having i reversed:- circulararc po'r tions' 2;:interengaged: =i1rsu rface contact to transmiti.blow-back forces-and move" the breech-'blockto the'front-of carried by said link for retracting and locking the firing pin upon initial movement ofithezoperating'arm before the breech-block -;is.-un;locked from the firing position 5. In a, firearm, the combination of a'receiver,

.a breech-block member and an operating arm member reciprocally carried by-thereceiver, a

:firing pin carried by the breech block, -:a pocket zinrone side of thereceiver, a, shoulder at the rear end of thepocketlfacing forwardly and outwardly to'form a seat, continuously engaging and .rmating. complementary. ,curved camsurfaces on said members havingreversed circularearcgportions. interengaged in surface contact to .transemit blow back: forces when .thenembers are moved rearwardly of the pocket in the receiver and which slide over one another, to seat and lock the breech -b1ockmember in, thefiring posi- ;ti on do said nocket,-;a link having spacedQstnb ;shafts mivetallv r onn ctine said mem s 1 munitting e mited relative, movement therebetween, :saiid linkrpivoting onthecenters from which the cam surfaces aregenerated, andmeans on the breecheblQ-Qklink-shaft for retracting and locking :the gfiring (pin upon initial movement of the operating 1arin ,before the breech-block is unlocked, from, the firing position.

v.6. In-:a-;firearrn,;the combination of a receiver havingga chamber, a.; barrelsecured to the front end ;,of the receiver, a breech-block slidably mounted .to; reciprocate longitudinally-within the ;chamber ;aof the receiver, a pocket on one side 10ft the receiver chamber tapering from adjacent the barrel, a shoulder at the 'rear end of ,the pocket facing forwardly and outwardly toward thercharrrbeng azreciprdcating; breech-block operating. armgslidablygsupported:by the receiver on .theppposite side ,of the chamber from the pocket, ;a link having; spaced, stub shafts pivotally-connecting the rearef,thetbreech-bloek with said .arm,iw ndrasurface-on;said operating arm to transmit -,blow back forces and toengage and move the;, breech-lol o ck v forwardly and force the rear, end, thereof into the ,;pocket and ,into seat- ,ing engagement with the shoulder, when the front end of,,tl 1e,,breech-b1ock is in engagement with the front ,wall of the" receiver, in its firing positiong said linkwithdrawingthe breech-block from chamber, a reciprocating t breech-block operat- -;ing: arm slidably; supportedqby the, receiver ,on

Y the opposite side of the chamber from the pocket,

a.;linkyhaving spacedstub; shafts pivotally conneoting the rear of V ,'the;,breech-b1ock with said .arm,- a--surface on said operating arm to trans- .imit blow; back forces and; to 'engageand move ,50'

gendthereofinto the -pocket and into seating en- ;gagement.-with the-.shoulder-when the front end ofithe breech-block is ,;in-engagement with the thQvbPChirb1QGk forwardlyand force the rear front-wall of .the receiver in its firing position, said linkwithdrawing, the breech-block from the shoulder andaetractinggit rearwardly in the receiver .chamber-when-saidoperating arm is reatracted-ra-nd means, on; ne rth l n e ubrshaft pivoted in the breech-block for holding theg-firingapin in I its retracted position when the operating arm. swings saidlink.

rIn afirearm ithe cornbination, of, a. receiver havingragchambema barrel-secured togthe front end ofqthe receiver, ,aybreech-block slidably mounted to reciproeate;longitudinally within- ;the ;chamber offithe; receiver, a.firing,pin carried by the zbreechgblockma pocket. on. one side of the receiver g-chamber 1 tapering from. adjacent. the .barreL, a shouldergahthe rearend- .of, the pocket facing forwardly and outwardly toward the chamber,,- av ;reqiprocating. breech-block operatills-z arm slidably supportedby the. receiver 'on t e oppo e,s ep rthe-chamber from th ke 3 -5, he t p link vrn r a 'i eden nd n lsh f a e 2 Jr, in:

Quo ed; in sa ar n-ana the other shaft pivotally mounted in the breechblock, a surface on said operating arm arranged to transmit blow back forces and to engage and move the breech-block forwardly and force the rear end thereof into the pocket and into seating engagement with the shoulder when the front end of the breech-block is in engagementwith the front wall of the receiver in its firing position, said link withdrawing the breech-block from the shoulder and retracting it rearwardly in the receiver chamber when said operating arm is retracted, a shoulder on the firing pin, and a cam face on the link shaft in the breech-block arranged to engage the shoulder on the firing pin to retract and hold it from firing when the operating arm swings said link.

9. In a firearm, the combination of a barrel, 7

a receiver secured to the barrel and provided with a chamber, a breech-block member mounted in the chamber for longitudinal reciprocation therein, a pocket in the receiver and tapering forwardly to the barrel, a shoulder at the rear end of the pocket facing forwardly and outwardly toward the chamber to form. a seat, an operating arm member for the breech-block mounted adjacent the opposite side of the chamber from the pocket, continuously engaging and mating, complementary cam surfaces on the members having reversed circular-arc portions interengaged to transmit blow back forces when the members are retracted rearwardly and which ride upon one another to seat and lock the breech-block member when moved into the pocket, and a link having spaced stub shafts pivotally connecting said members permitting limited relative movement therebetween, said link pivoting on the centers from which the cam surfaces are generated, the combined action of said cam surfaces and said link being arranged to force the rear end of the breech-block member on the shoulder and lock it in firing position when the front end of the breech-block member is in engagement with the front wall of the chamber and to unlock and retract the breech-block to' the rear of the chamber.

10. In a firearm, the combination of a barrel, a receiver secured to the barrel and provided with a chamber, a breech-block mounted for longitudinal reciprocation in the chamber, an action arm arranged to lock the breech-block in the firing position, means defining a firing pin bearing disposed longitudinally in the breechblock, a firing pin operable therein, means defining ,a second bearing disposed normally to and intersecting the firing pin bearing, a shoulder on the firing pin adiacent the second bearing, and means operated by said action arm and journaled in the second bearing to swing and engage said shoulder and prevent the firing pin from operating as the action arm retracts.

11. The structure of claim 10, characterized in that said last mentioned means comprise a shaft having a notched section that permits movement of the firing pin when the breech-block is locked and engages said shoulder when the breech-block is unlocked.

12. In a firearm, the combination of a receiver, having a chamber, a barrel secured to the front end of the receiver, a breech-block slidably mounted to reciprocate longitudinally within the chamber of the receiver, a forwardly and outwardly facing seat on one side of the receiver chamber to be engaged by the breechblock when locked in firing position, a reciprocating operating arm slidably supported by the receiver, a bearing in the breech-block, a bearing carried by the operating arm, a link having spaced depending shafts journaled in the bearings of the breech-block and the operating arm for retracting the breech-block from said seat, and continuously engaging and mating complementary interengaging cam means of reversed curvature on the breech-block and the operating arm for transmitting forces therebetween and for seating and locking the breech-block on said seat. a p

13. The structure of claim 12 which also includes a firing pin carried by the breech-block, a shoulder on the firing pin adjacent the bearing in the breech-block, and means on the shaft in said last mentioned bearing for preventing the operation of the firing pin when the link swings before retracting the breech-block from said seat.

14. The structure of claim 12 which alsoincludes a firing pin carried by the breech-block, means efiective by the rotation of the shaft in said bearing for locking and unlocking the firing pm.

15. In an automatic firearm, the combination of a barrel. a receiver secured to the barrel and provided with a chamber, a breech-block member mounted in the chamber for longitudinal reciprocation therein, a pocket in the receiver and tapering forwardly to the barrel, a shoulder at the rear end of the pocket facing forwardly and outwardly toward the chamber, an action arm member slidably mounted in the receiver on the side opposite to the pocket, continuously en- ;gaging and mating complementary cam surfaces on the members having reversed circulararc portions interengaged in surface contact to transmit forces therebetween when the members are retracted rearwardly of the pocket, the curved portion of the cam surface on the action arm member being positioned behind the curved cam surface on the breech-block member when retracted, the curved cam surfaces riding upon one another to force the rear end of the breechblock member into the pocket and into seating engagement with the shoulder when the front end of the breech-block'member is in engagement with the front wall of the chamber and when on top of one another to lock the breechblock member in firing position. and a link pivotally connect d to each of said members on center points from which the convex portions of said cam surfaces are enerated to continuously maintain the cam surfaces in contact.

16 The structure of claim 15 which also in cludes a firing pin carried by the breech-block,

and means actuated by the swinging movement of the link to retract the firing pin when the action arm member is unlocking the breechblock before it is unseated.

RUSSELL J. TURNER.

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

UNITED STATES PATENTS Num er Name Date 289.972 Burgess Dec. 11, 1883 317,162 Maxim May 5, 1885 544.657 Browning Aug. 20, 1895 545,672 Browning Sept. 3, 1895 (Other references on following page) Number 11 UNITED STATES PA'I'ENTS Name Date Browning Feb. 22, 1898 Mannlicher May 19, 1903 Freeman May- 30, 1905 Bernard Oct. 31, 1905 Mauser Dec. 17, 1912 Osborne Oct. 28, 1913 Swebilius et a1. Mar. 28, 1916 Number 1.2 Name Date Squire et a1 Sept. 30, 1919 Cox Oct. 12, 1920 Horan Jan. 9, 1923 Fearn July 10, 1923 Holek Sept. 1, 1931 Browning Apr. 9, 1940 Horan Feb. 15, 1944

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