US2372339A

US2372339A - Self-loading firearm

Info

Publication number: US2372339A
Application number: US459749A
Authority: US
Inventors: William C Roemer
Original assignee: Western Cartridge Co
Current assignee: Western Cartridge Co
Priority date: 1942-09-26
Filing date: 1942-09-26
Publication date: 1945-03-27
Anticipated expiration: 1962-03-27
Also published as: GB570663A

Description

March 27, i945. w. c. ROEMER 2,372,339

SELF-LOADING FIREARM Filed sept. 2e, 194.2V 2 shts-sheet 1 mm. mm

March 27, i945. w. c. RoEMr-:R 372,339

SELF-LOADING FIREARM I Filed sept. 2e, 1942 2 sheets-Sheet 2 Patented Mar. 27, 1945 UNlTED STATES PATENT OFFICE SELF-LOADING FIREARM William C. Roemer, New Haven, Conn., assignor to Western Cartridge Company, New Haven, Conn., a corporation of Delaware Application September 26, 1942, Serial N o. 459,749

9 Claims.

The present invention relates to improvements in rearms, and relates more particularly to improvements in self-loading firearms,'i. e., rearms in which the forces developed by the discharge of a given cartridge effect the extraction and ejection of the just-fired cartridge preparatory to the automatic reloading of the rearm with a fresh cartridge.

One of the objects of the present invention is to provide a self-loading firearm with superior means for effecting the actuation of the breechbolt thereof as a result of the discharge of a cartridge.

Another object of the present invention is to provide a self-loading firearm with superior means for guiding the action-slide or its equiva.

lent during the operation of the firearm.

A further object of the present invention is to provide a superior self-loading firearm in which provision is made for the accurate guiding of the connecting-means between the piston and the breech-bolt, without requiring the undue weak ening of the barrel of the rearm.

Still another object of the present invention is to provide a superior self-loading firearm with breech-bolt-actuating means which is both durable and rugged in its operatiombut which may be readily and conveniently dismounted to permit inspection and cleaning.

With the above and other objects in View, as will appear to those skilled in the art from the present disclosure, this invention includes all features in the said disclosure which are novel over the prior art and which are not claimed in any separate application.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. l is a broken view of the central portion of a self-loading repeating rearm embodying the present invention and showing the same partly in side elevation and partly in vertical centrallongitudinal section, with the parts in the positions which they assume at the instaont of the discharge of the firearm;

Fig. 2 is a broken view in vertical central-longitudinal section of the portions of the firearm adjacent the cylinder-lug of the barrel, and with the parts in their normal at-rest positions;

Fig. 3 is a similar view but showing the piston i and action-slide at the limit of their respective rearward movements following the discharge of the firearm;

Fig. 4 is a broken view in rear elevation of the receiver and trigger-plate;

Fig. 5 is a transverse sectional view taken on the line 5 5 of Fig. 2;

Fig. 6 is a similar view but taken on the line 6 6 of Fig. 2;

Fig. '7 is a broken view in vertical central-longitudinal section of the forward portions of the receiver and trigger-plate and the rear portion of the guide-rod;

Fig. 8 is a transverse sectionalview taken on the line 8 8 4of Fig. 7;

Fig. 9 is a similar view taken on the line 9 9 Of Fig. 7;

Fig. 10 is a'broken underside view of the for-A ward portion of the receivertogether with the rear portion of the barrel;

Fig. l1 is abroken top or plan view of the forward portion of the trigger-plate;

Fig. 12 is aperspective view cf the guidegrod, detached;

Fig. 13 is a similar view of the cup-shaped piston, deatched; and

Fig. 14 is a perspective view of the action-slide, detached.

The particular self-loading rearm-structure illustrated in the accompanying drawings,` comprises in the main a receiver 22, a barrel 23,- a

trigger-plate 24 and a reciprocating action-slide 25. The receiver 22, trigger-plate 24, barrel 23 and action-slide 25 are preferably formed of high-grade steel to afford maximum strength and minimum weight.

At its rear end, the barrel 23 is rigidly connected in any suitable manner to the forward end of the receiver 22, which latter is formed intei riorly with a mechanism-receiving chamber 26 accommodating varios features of the rearmmechanism. The features of the mechanism within the mechanism-receiving chamber 26 do not require detailed description herein other than to note that the said mechanism includes a reciprocating breech-bolt 21 which also has oscillatory movement in the chamber 26 of the receiver 22 in a manner broadly similar to the breech-bolt of the well-known Garand rie.

Adjacent its rear end, the barrel 23 is formed with an integral depending cylinder-lug 28 which" is formed with a rearwardly-opening piston-v end of the relatively-small forward portion 3| of the piston-chamber 29 is a gas-passage 32 communicating at its forward end with the bore 33 of the barrel 23, so as to conduct gas under pressure from the said bore to the piston-chamber 29 for purposes as will hereinafter appear.

Reciprocating in the piston-chamber 29 is a cup-shaped .Y pistongenerally .designated by the reference character34and comprising-a. relative#- ly-large cylindrically-contoured rear portion 35 and a relatively-small cylindrically-contoured forward portion 36. The respective rear and

forward portions

35 and 35 of the piston134 yreciprocate with a smooth sliding trespectively in the portions 30 and 3| of thefpi'ston-chamber29.

The cup-shaped piston `3l! is'forrned .with a rearwardly-opening cylindrioally-contoured socket 31 receiving with a sliding fltfthe stemx 38 of a guide-rod 39. The said guide-rod is arranged coaxially with respect to the central-longitudinal axis: of the` lpistonzt2 9-eandeextends :in substantial parallelism with the longitudinal, axisofLthebarre1l23. At its trear" end; `theflovverzporton .of the guide-rod 39 is formed with a flangealikaanchoringeheadr-40" whichzisfof substantially; semicircu- 'lar form ,f andnvhich risfflocapted.` directly below a ,clearance-notch? 4 I :formedainzthe'upperirearfportion of the guide-rod 39, as is shownfparticularly wellt-tinLFig. i12.' :Thelowerxrearvrportion of'the guide-rod 39 lying immediatelyforwardlygofrits anchoring-'head 40.1s accommodated :in :an Supwardly-opening longitudinally-extending .groove 421 formed inttherforwardmortiom of the? `triggerplate .24 and .intersectingthewforwarda edge of" ,the

said trigger-plate. The ranchotlng-:headr-AU #of l" the guide-rod i 39 isf seated Tinian -upwardly-,opening anchorin'gerecess miiformedln'ithe .triggeranchoring-recessf43l`thetrigger-plate'24'lisformed f with a forwardlyefacing.stop4ab11tment45' against which is seated the rear face of .th'elguide-irodz39, which .latter 'is yfthus 'hel'daagainst rearward-.- displacement. The 'fonward fdisplacernent of vthe guide-'rod'39 is prevented by the coaction of its anchoring-head. v40 withthefforward `wa1lo`f the anchoring=recess '43.

'(Dnweach of its respective foppos'itesid'esfadjacent its` forward' end, ltheiireceiver22 is` formed with onel offtwo` 'downwardly'-extendingilaterallyperforated f coupling-'ears JAB-146 'lfbetweenfwhich is Areceived z av coupling-ear 'S41 extending upwardly from `tlfiefor-ward` portionrofltheftrigger-.platekZL asrisiespecially wellishown in'lFig.- 8. :Extending transversely through :.theiicoupling-ears :.46-46 and :41 '.is Ta couplingepinm which =is1lyieldingly retained in vpla'celby-a detent-'spring.;49r and -wliich serves '.'to `couple together :the :respective forward portions -of ftherreceiver :.22 fand ftrigger-platef24. When the :assemlolyisy mountedzlinlafstock in the usual;;manner:ofrearms, such afsto'ck will nor-l mally ccover the might vfend of :the .',coupling-pin 48 Y,andfpostively prevent its faxialfdisplacement to ,'.the right. VAs thusw constructedz'and z arranged;

-any longitudinal shocks applied to'theeguide-rod :39rareztakenupby;the1tri'ggerplate24Jandthence transmitted by the coupling-pin 48 to the forward portion of the receiver 22.

At its rear end the trigger-plate 24 is formed with an upwardly-extending rib 50 which is formed on each of its respective opposite Sides with one oi two longitudinal coupling-grooves 5l-5i, each of which receives with a sliding fit one of two laterally-spaced-.apart coupling-ribs 52--52 :extending inwardly Vin opposite directions respectively from each of the opposite sides of the rear portion of the receiver 22, as is especially well shown in Fig. 4.

The action-slide 25 before referred to is formed at its forward end with a head 53, from the upvperright hand portion of which rearwardly extends an integral side-bar 54 which latter terminates at its rear in an outwardly-extending operating-l'iandler 55,as is especially well shown in Fig. 14. In its inner face, just forwardly of its operating-handle 55, the side-bar 54 of the action-slide25 is formed .Withvafcamfrecess 56-into 4which lits-.a llug 51 laterallyioff-setting.fromtthe and normally covering thexbottnmzand vsideszof the cylinder-lug 28 anduarportion-.of the'sides of the Ybarrel 23.

The end-wall'v 58 :ofthe-'aheada53 =off/the yactionslide 25 iszforrned'centra-lly Withaflongitudinallyextending bearing-passage i :which :isiproportioned to L receive with favfreel sliding fit thelrmain intermediate portioni'off the guide-rodfll. Bearing against the .forwardzfacepf thenend-wall' 58 around the bearing-passage 60 vis 1 the "reariend of the cup-shapedfpistont34,iwhich vlatter-functions to drivethexactioneslme .25x1earwardly to effect the operation. of fthe breech-bolt 21 in fa manner as will hereinafterzappear.

For the purpose'of'yieldingly .urgingithe actionslide 25 forwardlyyinto.itsforemostI position and hence also moving the .breech-bolt 21 into its `breech-closing position, a helical breech-closing spring 5l is employed. The 'forward portion of the said breech-closing spring "6| encircles a breech-closing -plun'gerfl62. 'Il'reire'ar'portion 0f the breech-closingispring'6| `fits Within va forwardly-openingspringchamber :B3 :extending longitudinally of the Ii1earm'structure and 'removably secured to the 'receiver ZZJzbeneatha Alongitudinalrib 54 formedintegralwith'an'd projecting laterallyfromnthe:right `side ofithef'sa-d receiver, adjacent the loweredgeithereof.

The rear end Tof the :breech-closing spring '6l thrusts against the rearaendawallofithezspringchamber 63, and 'at its forward iend the `said spring thrusts against the rear face o'f a collar formed integral `withtl'le 'forwardgportion Vof the breech-closing plunger i92 :and thrusting at its forward faceagainstthe' rear faceof' the'endwall 58 of the head 53 of the action-'slideiz Normally the breech-'closing spring 6| 'acting through the breech-closing plunger 62 maintains the forward face `of thefend-.wallz ,of `the head 53 in engagement Withrthelreariendff'thepiston 34 and, in turn, maintains the forward end of the said piston against the front wall rof the piston-chamber 29, as is clearly shown in Fig. 2.

When the firearm is discharged, gas under pressure will pass downwardly and rearwardly from the bore 33 of the barrel 23 and impinge against the forward end of the piston 34. Under these conditions, the piston 34 will be moved violently rearwardly until it is stopped by the engagement of the rear face of its end-wall with the forward end of the guide-rod 39, as is shown in Fig 3. The movement imparted to the piston 34 as just described will cause the said piston to, in turn, impart rapid movement to the actionslide 25, which latter will be thrown rearwardly against the tension of the breech-closing spring 5l until the rear face of its head 53 strikes the forward face of the receiver 22. The parts will now have reached the positions in which they are shown in Fig. 3.

During its rearward travel as above described, the action-slide 25 will, through the intermediary of its cam-'recess 56 and the lug 51 of the breechbolt 21, effect the unlocking and retraction of the said breech-bolt. This movement Will in -the usual manner of firearms, effect the extraction and ejection of the just-fired cartridge. Also, during the rearward movement described, the forward portion of the action-slide 25 willbe guided by the sliding of the surface of the bearing-passage 60 in its head 53 upon the periphery of the stationary guide-rod 39.

Following the completion of the actions just above described, the breech-closing spring 6| will at the rear end of the receiver 22. A s the triggerplate is moved rearwardly as described, it will also carry with it the guide-rod 39, but due to the clearance-notch 4| formed in the said guiderod, such movement will not be interfered with by the receiver 22.

The trigger-plate 24 may be now completely removed from the structure, following which vthe guide-rod 39 may be removed by springing its rear end downwardly and withdrawing it rearwardly from the bearing-passage 60 in the actionf slide 25 and from the socket 31 in the pistonf34. The springing-down of the rear end of the guiderod 39 as just described is permitted not only by Vits own iiexibility but by the freedom of fit which it has with reference to both the bearing-passage 60 and the socket 31.

Following the removal of the guide-rod 39, the action-slide 25 may be dismounted from the rearrn and the piston 34 may be withdrawn rearwardly from the piston-chamber 29 in the cylinder-lug 28.

The invention may be carried out in other specie ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. and all changes coming within the meaning and equivalency range o f the appended claims are intended to be embraced therein.

ton-chamber of the said cylinder; a guide-rod formed separately from and arranged substantially coaxially with respectl to and` extending rearwardly from a point adjacentthe said piston and supported at its rear end by the said receiverunit, a forward portion of the said guide-rod being positioned to be engaged by and to positively stop the rearward travel of the said piston; a breech-bolt movable in the said receiver-unit; and an action-slide movable independently of both the said piston and the said guide-rod and provided with a guide-portion having sliding l bearing on the said guide-rod at a point longitudinally intermediate the said piston and the point at which the said guide-rod is supported by the said receiver-unit` the said guide-portion being positioned to be engaged by the said piston at a point longitudinally intermediate the said piston and the point at which the saidvguide-rod is s"up ported by the said receiver-unit, the said guideportion being positioned to be engaged by the lsaid piston and driven rearwardly thereby beyond the point at which the rearward movement of the said piston is halted by the said guide-rod, the saidaction-slide being operatively connected to the said breech-bolt to move the same.

2. A self-loading firearm-structure of the type wherein a gas-operated piston is confined to a stroke materially less than the stroke of a breech-bolt which the said piston actuates, including in combination: a receiver-unit; a breech-bolt reciprocating in the said receiverunit; a barrel projecting forwardly from the said receiver-unit; a cylinderprojecting laterally from the said barrel and having a rearwardly-opening piston-chamber eccentrically located with respect tothe bore of the said barrel andV communicating with the bore of the said barrel; a piston reciprocating in the piston-chamber of the said cylinder; a guide-rod formed separately from and arranged substantially coaxially with respect to the said piston and having its forward end telescopically supported by the said piston and having its `rear end supported by the said receiver-unit, a forward portion of the said guiderod being positioned to be engaged by and to positively stop the rearward travel of the said piston; and an action-slide movable independently of both the said piston andthe said guide-rod a-nd operatively interconnecting the said piston and the said breech-bolt and provided with a guide-portion having sliding bearing on the said guide-rod at a point longitudinally intermediate the `said piston and the point at'which the said guide-rod is supported by the said receiver-unit,

the said guide-portion being positioned to be engaged by the said piston and driven rearwardly thereby beyond the point at which the rearward movement of the said piston is halted by the said guide-rod.

3.' A 'self-loading firearm-structure of the type wherein a gas-operated piston is confined to a stroke materially less than the stroke of a breech-bolt which the said piston actuates, ihcluding in combination.: a receiver-unit; a breech-bolt reciprocating in the said receiverunit a barrel projecting forwardly from the said receiver-unit; acylinder4 projectingA laterally from the said barrel and having a rearwardlyopening piston-chamber eccentrically located with respect to the bore of the said barrel and communicating with the bore of the said barrel; a rearwardly-opening cup-shaped pistonrreciproeating in the piston-chamber of the saidy cylinder; a guide-rod formed separately from and arranged substantially co-axially with respect to the said cup-shaped piston and having its forwardv end extended into the said cup-shaped piston and having its rear end supported by the said receiver-unit, a forward portion of the said guide-rod being positioned to be engaged by and topositively stop thel rearward travel ofthe said piston; and an action-slide movable independently of both the said piston and the said guide-rod and operatively interconnecting the said cupshaped piston and thesaid breech-bolty and provided with a guide-portion having sliding bearing on the said guide-rod at a point longitudinally intermediate' the said piston and-the point at which the said guide-rod is supported by the said receiver-unit, the said guide-portion being positioned to be engaged by the said piston and driven rearwardly thereby beyond the point at which the rearward movement of the said piston is halted by the said guide-rod.

4. A self-loading firearm-structure of the type wherein a gas-operated piston is confined to a stroke materiallyI less than the stroke of a breech-bolt which the said piston actuates, including in combination: a receiver-unit;` a breech-bolt reciprocating in the said receiverunit; a barrel projecting forwardly from the said receiver-unit; a cylinder projecting laterally from the said barrel and having a rearwardlyopening piston-chamber eccentrically located with respect tothe bore -of the said barrel andv communicating with the bore of the said barrel; a rearwardly-opening cup-shaped piston reciprocating inthe piston-chamber of the said cylinder; a guide-rod formed separately from and arranged substantially co-axially with respect to the said cup-shaped piston and having its forward end extended into the saidy cup-shaped piston and vhav-ing its rear end supported: by thesaid receiver-unit, a forward portion of the said guide-rod being positioned to be engaged by and to positively stop the rearward travel of the said piston; and an action-slide movable independently of both the said piston andthe said guide-rodv4 and operatively interconnecting the said breechbolt and the said piston and provided with a' guide-portion engaged by the open rear end of the said cup-shaped piston and having slidingbearing on the said guide-rod ata point longitudinally intermediate the said piston and the point at which the said guide-rod 'is supported by the said receiver-unit, the said 4guide-portion being positioned to belengaged by thesaid vpiston and driven rearwardly therebyv beyond the point at which the rearwardmovement ofthe said piston is halted by the said guide-rod.

i 5. A self-loading Firearm-structure of the type wherein a gas-operated piston is confined to a stroke materially less than the stroke of a breech-bolt which the said piston actuates, in'- cludng in combination: a receiver-unit; a barrel projecting forwardly from the said re.- ceiver-unit; a cylinder projecting. laterally from astra-ssa thesaid barrel 'and having a.Y rearwardly-opening piston-chamber yeccentricallyl located with respect to the bore of the saidj barrely and communicating with theV bore4 of the said barrel; a piston reciprocating, in the piston-chamber of the said cylinder; a normally-stationary guide-rod formed separately froml and arranged substantially coaxially.v with respect to andy extending rearwardly from a point adjacent the said piston and anchoredi at its rear'in the said receiver-unit, a forward" portion of the said guide-rod being positioned toibe engaged by and to positively stop the rearward travel of the'said'piston; a breech-bolt movable in the said receiver-unit; and an actionslide movable independently of both the said piston; and the said guide-rod and operatively interconnecting the said piston and the said breechbolt andfprovided with a guide-portion having sliding bearing on said guide-rod at a point longitudinally intermediate the said piston and the point at which the said guide-rod is supported by the said'` receiver-unit, the said guide-portion being positioned' to be. engaged by the said piston and driven rearwardly thereby beyond the point at which the rearward movement of `the said pistonis halted by the said guide-rod.

6. A self-loading rearm-structure of the type wherein a gas-operated piston is confined to a stroke materially less than the stroke of a breech-bolt which the' said Vpiston actuates, includingin combination: a receiver; a breech-bolt movable in the said receiver; atrigger-plate removably secured to the underside of the said receiver;. a barrel projecting forwardly from the said receiver; cylinder projecting laterally from the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a piston reciprocating in the piston-chamber of the said cylinder; a guiderod formed separately'from and arranged substantially coaxially with respect to and extendin-g rearwardly from the said piston, a forward portion of the said guide-rod being positioned to be engaged by and' to positively stop the rearward'travelv of the said pistonl the said guide-rod being held at its rearl between an upper portion of the said trigger-plate and a `lower portion of thek said received and being releasable from the gun-structure by iirst `detaching the said triggerplate from the said receiver; and an action-slide movable independently of both the said piston and the said guide-rod and operatively interconnecting the` said piston and the said breechbolt, the said action-slide being provided with a guide-portion having Asliding bearing on the said guide-rodI at a point longitudinally intermediate the said piston and the point at which the said guide-rod is held between the said trigger-plate and the said receiver; the said guide-portion being positioned vto be engaged by the said piston and driven rearwardly thereby beyond the point atz'which the rearward movement of the said piston ishaltedby thesaid guide-rod.

7. AYself-loading firearm-structure of the type wherein-'a gas-operated`- piston is confined to a stroke materially less than the stroke of a breech-bolt which the said piston actuates, including in. combination: a receiver; a breech-bolt movable in the said receiver; a trigger-plate removably secured to the underside of the said receiver; a barrel projecting `forwardly' from the said receiver;` `a cylinder projecting laterally from the. said barrel and having a rearwardly-opening piston-chamber communicating with thev bore of the said barrel; a piston reciprocatingin the piston-chamber of the said cylinder; a guide-rod formed separately from and arranged substantially coaxially with respect to the said piston and having its forward end telescopically supported thereby, a forward portion of the said guide-rod being positioned to be engaged by and to positively stop the rearward travel of the said piston, the said guide-rod being held at its rear between an upper portion of the said trigger-plate and a lower portion of the said receiver and being releasable from the gun-struc ture by rst detaching the said trigger-plate from the said receiver; and an action-slide movable independently of both the said piston and the said guide-rod and operatively interconnecting the said piston and the said breech-bolt, the said action-slide being provided with a guide-portion having sliding bearing on the said guide-rod at a point longitudinally intermediate the said piston and the point at which the said guide-rod is held between the said trigger-plate and the said receiver, the said guide-portion being positioned to be engaged by the said piston and driven rearwardly thereby beyond the point at which the rearward movement of the said piston is halted by the said guide-rod.

8. A self-loading firearm-structure of the type wherein a gas-operated piston is confined to a strokeY materially less than the stroke of a breech-bolt which the said piston actuates, including in combination: a receiver; a breech-bolt movable in the said receiver; a, trigger-plate removably secured to the underside of the said receiver; a barrel projecting forwardly from the said receiver; a cylinder projecting laterally from thesaid barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a rearwardly-opening cup-shaped piston reciprocating in the piston-chamber of .the said cylinder; a guide-rod formed separately from and arranged substantially coaxially with respect to the said cup-shaped piston and having its forward end extending into and telescopically related to the said cup-shaped piston, a forward portion 0f the said guide-rod being positioned to be engaged by and to positively stop the rearward travel of the said piston, the said guiderod having its rear end held between an upper portion of the said trigger-plate and a lower portion of the said receiver, the said trigger-plate and the said guide-rod being constructed and arranged so that the said guide-rod is supported at its rear by the said trigger-plate and is releasable from the gun-structure by first detaching the said trigger-plate from the said receiver; and an action-slide movable independently of both the said piston and the said guide-rod and operatively interconnecting the said cup-shaped piston and the said breech-bolt, the said action-slide being provided awith a guide-portion having sliding bearing on the said guide-rod at a point longitudinally intermediate the said piston and the point at which the said guide-rod is held between the said trigger-plate and the said receiver, the said guide-portion being positioned to be engaged by the said piston and driven rearwardly thereby beyond the point at which the rearward movement of the said piston is halted by the said guide-rod.

9. A self-loading firearm-structure of the type wherein a gas-operated piston is conned to a strokel materially less than the stroke of a breech-bolt which the said piston actuates, including in combination: a receiver; a breech-bolt movable in the said receiver; a trigger-plate removably secured to the underside of the said receiver; a barrel projecting forwardly from the said receiver; a cylinder projecting laterally from the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a rearwardly-opening cup-shaped piston reciprocating in the piston-chamberv of the said cylinder; a guide-rod formed separately from and arranged substantially coaxially with respect to the said cup-shaped piston and having its forward end extending into the said cupshaped piston, a forward portion of thesaid guide-rod being positioned to be .engaged by and to positively stop the rearward travel of the said piston, the said guide rod having its rear end held between an upper portion of the said trigger-plate and a lower portion of the said receiver, the said trigger-plate and the said guide-rod being constructed and arranged so that the said guide-rod is supported at its rear by the said trigger-plate and is releasable from the gunstructure by first detaching the said trigger-plate from the said receiver; and an action-slide movl able independently of both the said piston and the said guide-rod and operatively interconnecting the said breech-bolt and the said cup-shaped piston, the said action-slide being provided with a guide-portion having sliding bearing on the said guide rod at a point longitudinally intermediate the said piston and the point at which the said guide-rod is held between the said trigger-plate and the said receiver, the said guideportion being positioned to be engaged by the said piston and driven rearwardly thereby beyond the point at which the rearward movement of the said piston is halted by the said guide-rod.

' WILLIAM C. ROEMER.