US2423854A - Head space adjusting and locking means for removable firearm barrels - Google Patents

Description

July 15, 1947. c. E. SIMPSON 2,423,854

HEAD SPACE ADJUSTING AND LOCKING MEANS FOR REMOVABLE FIREARM BARRELS Filed Dec. 17, 1945 2 SheetsSheet l W m Md m a F \i, E 7 E m V M A? g4? N, iifiN i N Q R wa a m y 9w H Q W 0 KW 1 N w camwamw- I Suez/"M44 July 15, 1&47. c. E. SIMPSON 2 5 HEAD SPACE ADJUSTING AND LOCKING MEANS FOR REMOVABLE FIREARM BARRELS Filed Dec. 17, 1943 2 Sheets-Sheet 2 'CLARENCEEEHMPEUN,

Patented July 15, 1947 HEAD SPACE ADJUSTING AND LOCKING MEANS FOR REMOVABLE FIREARM BARRELS Clarence E. Simpson, Springfield, Mass., assignor to the Government of the United States of America, as represented by the Secretary of War Application December 17, 1943, Serial No. 514,612

(Granted under the act of March- 3, 1883, as amended April 30, 1928; 370 0. 757) 9 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 improvement in firearms, more particularly to head space adjusting means and to means for enabling a quick change of barrels.

A very serious limitation in firearms of theautomatic type, particularly aircooled automatic firearms, is the overheating of the barrel from firing long continuous bursts of cartridges. Various means have been provided to overcome such overheating but such means have been only partially successful. The most satisfactory practice has been to change the overheated barrel for another cold, unused barrel.

In the heat of battle it is essential that a firearm be kept in operation until the crisis has passed. To do so, therefore, means that the hot barrel in an aircooled Weapon must be quickly detachable so that another barrel may be immediately replaced with a minimum loss of time in effecting such change. In providing such a quick change barrel there are numerous inherent difiiculties to be overcome in any firearm. Foremost among such difficulties is the accumulation of manufacturing tolerances in the various related components affecting headspace of the firearm. In fact, the manufacturing tolerance accumulations On components other than the barrels will be such that the distance from the head of a cartridge seated in the chamber of the barrel to the face of the bolt will var to such a degree that in some instances the bolt cannot be closed on a cartridge and hence the gun cannot be fired, while the other extreme is such that the face of the bolt 'does not support the head of the cartridge and therefore permits the case to be ruptured when fired.

In the past most quick change barrels for aircooled firearms utilized an interrupted thread on the breech end of the barrel to permit rapid changing of such barrels. With such a securing means the barrel frequently is insecurely held because of the non-rigid support afforded by an interrupted thread. Further, an interrupted thread system for fastening the'barrel precludes all possibility of incorporation therein of satisfactory adjustable headspace means.

Accordingly, it is an object of this inven'tion to provide a quick change barrel attachment for a firearm incorporating an adjustable headspacing feature to compensate for manufacturing tolerances of components afiecting headspace.

Anotherpbj'ect of this invention is to provide an improved combination barrel support and gas cylinder for a firearm.

Still another object of this invention is to provide a quick change barrel attachment for a firearm having a safety feature to prevent firing of a cartridge in the barrel when the barrel is not in the locked position. i

The specific nature "of the invention as well as other objects and advantages thereof will clearly a pear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is a partial longitudinal sectional view of a firearm showing the quick change barrel and headsp ace adjusting means.

Fig. 2 is a right end elevational view of Fi 1.

Fi 3 is a detail view partly in longitudinalsection showing the barrel in the locked position.

Fig. 4 is across sectional view taken along the plane 4# of Fig. 1.

Fig. 5 is across sectional view taken along the plane 5--5 of Fig. 1.

Fig. 6 is a cross sectional view taken along the plane 6-6 of Fig. 1.

Fig. 7 is a fragmentary detail right side view of the firearm showing the slide blocking plunger and plunger spring.

This in vention essentially comprises a barrel, a barrel locking sleeve and a barrel locking handle. The barrel locking sleeve is threaded and is screwed into the receiver of a firearm and becomes a permanent part of the receiver. Two locking lugs are provided on the interior of the sleeve which engage corresponding locking lugs provided on the barrel when the barrel is inserted thr'u thesleeve and such sleeve is rotated approximately a quarter turn. This brings the locking lugs in the sleeve into contact with the locking lugs on the barrel. Headspace adjustment is readily accomplished by slightly rotating the sleeve within the receiver in a clockwise or counterclockwise direction as necessary by means of thebarrel locking handle.

In Fig. 1 there isishown in asse'mbledrelation a firearm embodying this invention. 'A'b'arrel I is mounted in a sleeve til which is in turn mounted in a receiver 15. The sleeve I0 is a short tubular member provided with a left hand threaded .portion 2 on its outer periphery. A collar 3 is provided integral with and adjacent the threaded portion 2. On the collar 3 2. lug 4 (Figs. 2 and 4) is provided to serve as a stop 'for a purpose to be described. An annular groove 5 is also provided about the periphery of sleeve llwhich is engaged by a barrel locking handle screw 6 in a manner to be described. On the interior surface of barrel sleeve I two oppositely disposed locking lugs 1 (Fig. 6) are provided. Barrel sleeve I0 is screwed into a suitably left hand threaded hole in receiver The barrel I is provided at the breech end with two oppositely disposed locking lugs 8 (Figs. 3 and 6). A short distance to the right of locking lugs 8 as viewed in Fig. 1 there is provided an enlarged diameter portion 9 on barrel I which forms a shoulder I I. Approximately in the center of the enlarged diameter 9 of barrel I a shallow annular groove I2 is provided which is engaged by a spring. biased plunger I3 of a barrel carrying handle IE to be described.

An operating member comprising a barrel locking handle I! (Figs. 2, 4 and 5) is placed over the end of barrel sleeve I0 provided with the annular groove 5 and abuts collar 3 on barrel sleeve Ill. The barrel locking handle I'I comprises a ring or sleeve portion I8 which surrounds barrel sleeve I0 and has an integral arm I9. Where arm I9 joins the ring portion I8 a small rectangular enlarged portion 2I is provided. In the hub 2I a threaded hole 22 is provided to receive the barrel locking handle screw 6. The screw 5 engages in the annular groove 5 on sleeve IIJ functioning as a removable key to retain the barrel locking handle H in a fixed axial position on the barrel sleeve I6. A sector of the outer periphery of the barrel sleeve I0, adjacent each side of the roove 5, is provided with a plurality of teeth or serrations 26. The ring or sleeve I8 has an internal portion thereof, directl underneath the arm I9 of the handle I! (Figs. 4 and 5), provided with a dovetail slot 23 in which is inserted a key 24 having axially spaced groups of teeth or serrations 25 matching those on the outer periphery of the barrel sleeve I0 and adapted to engage the same to lock the handle I! in difi'erent selected positions of adjustment on the barrel sleeve I0 for the purpose of adjusting the headspace of the firearm in a manner to be described.

Approximately opposite hub 2| on the outer periphery of ring portion I8 there are provided serrations 21 for engagement by a spring biased wedge-shaped tooth 28" forming part of a resilient member 28 mounted in a transverse slot 28' in receiver I5 directly underneath barrel I (Figs. 1, 3, 4 and 5). The serrations 21 are provided to hold barrel locking handle I I in an upraised position, as shown in Fig. 5, to unlock the barrel I to permit the same to be readily withdrawn from receiver I5 in a manner to be explained. To hold the barrel locking handle I! in the locked or downward position, additional serrations 29 are provided on the outer periphery of ring I8, spaced approximately 90 from serrations 21, so as to engage wedge-shaped tooth 28" of the member 28 when handle I! is rotated approximately 90, as shown in Fig. 4. The integral lug 4 on the collar 3 strikes a stop 40 (Figs. 2, 4 and 5) on the receiver I5, when handle I1 is raised to the unlocked position of Fig. 5. Lug 4 is so positioned that the wedge-shaped tooth 28 on the member 28 will always engage one of the serrations 21 of handle Il when handle I! is raised to the unlocked position. The stop 40 comprises a pin forcibly driven into a suitable hole in receiver I5 susbtantially underneath ring I8 of handle I! as shown in Figs. 4 and 5.

The barrel carrying handle I6 (Fig. 1) comprises a bracket I4 and a grip 30. The bracket I4 is mounted on the enlarged diameter portion 9 of barrel I and is free to rotate thereon. The bracket I4 is retained on barrel I by the spring biased plunger I3 which engages the annular groove I2 on the enlarged diameter portion 9 of barrel I. A suitable notch 4I is provided in the groove I2 so that the handle I6 may be secured in an upright position to facilitate insertion of the barrel into barrel sleeve ID. A smart blow on the side of grip 30 will readily disengage plunger I3 from the notch however permitting the handle It to be rotated out of the line of sight of the firearm to a lowered position whereupon the plunger I3 will then engage another notch (not shown) thereby retaining the handle I6 at such a lowered position until forcibly re moved therefrom.

Barrel I is further supported by a barrel support bracket 3I (Fig. 1) which surrounds barrel I at a distance approximately one-third the length of the barrel from the breech end of the barrel. The bracket 3| is secured to barrel I as by a pin 32 and surrounds a gas port 33 in barrel I. The bracket 3| projects downwardly and is provided with a transverse hole 34 to receive the end of a gas cylinder tube plug 35. The gas cylinder tube plug 35 is secured to the end of a gas cylinder tube 39 as by threads 35a. The gas cylinder tube 36 is in turn rigidly secured in a suitable manner to the end of receiver I5. Thus the gas cylinder tube 36 thru the bracket 3| provides additional support to barrel I. A hole 31 provided in the bracket 3I communicates with gas port 33 in barrel I and with an axial hole 38 in gas cylinder tube plug 35 to admit a portion of the gases of combustion to the face of an operating piston 39 within gas cylinder tube 36, Piston 39 is suitably connected to an operating slide 43.

A plunger 42 (Figs. 4 and 7) in receiver I5 is provided to block operating slide 43 to prevent accidental discharge of the weapon when barrel locking handle I! is in the raised or unlocked position. One end of the plunger 42 is provided with a substantially oval-shaped head 44 slidably mounted in a similarly shaped transverse recess 45 in receiver I5, and the opposite end of the plunger 42 is slidably carried in an opening 42, also in the receiver I5 but positioned directly opposite to the recess 45, as shown in Fig. 4. Recess 45 communicates with the hollow interior of receiver I5. The plunger 42 is biased by a fiat spring 46 transversely of the receiver I5 to engage the handle I! when such handle is in the locked position as shown in Figs. 2 and 4. Spring 46 is horizontally mounted on the right side of receiver I5 as shown in Fig. '7 by a screw 41 which passes thru a slot 48 in one end of spring 46 and into a threaded hole in receiver I5. The other end of spring 46 bears against head 44 of plunger 42. Hence when handle I1 is not properly abutting the receiver I5. as in Fig. 4, the spring 46 biases the plunger 42 to the left, as viewed in Fig. 4, causing the head 44 to enter the hollow interior of receiver I5. The slide 43 is provided with a notch 43 and when in battery position this notch registers with the head 44. Thus, when the handle I7 is not in its final position, as shown in Fig. 4, the head of the biased plunger 42 enters the notch 43, thereby blocking slide 43 against longitudinal movement.

The firearm shown in Fig, 1 embodying the headspace adjusting feature and barrel previously described is readily adjusted for headspace in the following manner:

As shown in Fig. 1, the barrel lugs 8 fully engage lugs I of barrel sleeve I0. As the sleeve I0 abuts barrel shoulder II, any rotational movement of sleeve I would produce a longitudinal movement of barrel I proportional to the lead of the thread of sleeve I0 either to the right or left as viewed in Fig. 1 depending upon the direction of rotation of sleeve I0. As such longitudinal movement of barrel I can be obtained b rotating sleeve II] the headspace of the firearm can thereby be readily adjusted.

To adjust the headspace of the firearm, the barrel locking handle I! is raised as shown in Fig. 5. A conventional headspace gage (not shown) .or a cartridge 60 of known dimensions is inserted in the chamber. The barrel locking handle I! is then rotated downwardly until arm I9 strikes the corner of receiver I5, as in Fig. 4. If handle .I"i cannot be lowered to this position the headspace is, therefore, too tight and barrel I cannot be locked into receiver I5. Handle I? is then raised, barrel I is moved slightly forward, screw 6 is unfastened, and handle I? is moved axially to the right as viewed in Fig. 1, until serrations '25 on the key 24 no longer engage the serrations 26 on the sleeve Iii. Handle IT, and hence the ring or sleeve I8, is rotated slightly in a clockwise direction, as viewed in Figs. 2, 4, and 5, relative to the barrel sleeve Iii until the serrated portion 25 is advanced one or more serrations relative to the serrated sector 26. Thereupon, handle I 'I and sleeve II] are again axially moved 'to the left, as viewed in Figs. 1 and 3; whereupon the barrel I can be moved back to its original position. If handle IT can be lowered to the closed position so that arm is strikes the corner .of the receiver It the firearm will be correctly headspaced. If not, the procedure of moving the serrations 25 of the key 2d relative to the serrated sectors 26 is repeated until handle I! can be rotated to its proper locking position shown in Fig. 4. It will'be appreciated that this indication of proper headspace adjustment is dependent upon the face of the bolt, when in full battery position, engaging the end of the headspace gage or cartridge in the chamber of the barrel. Conversely if handle I'I closes too easily when headspace adjustment is first made the headspace is too great and a similar procedure must be repeated until barrel locking handle II will just close. In this case however sleeve I8 is rotated in a counterclockwise direction, as viewed in Fig.

2, relative to the barrel sleeve Iii. When handle I1 is properly adjusted relative to the barrel sleeve I0, screw 6 is turned in so that the end of such screw engages the walls of groove thereby securing sleeve I0 and handle I! against relative axial displacement. The wedge shaped tooth 28" on the spring member .28 engages serrations 21 to hold handle I! in the raised position, after unlocking barrel I from sleeve It, preparatory to receiving the same or a new barrel. The member 28 through its tooth 28" also retains handle IT in the locked position and against accidental movement by engagement with one of the serrations .29as previously mentioned.

Barrel I is rapidly changed by raising handle II until lug strikes stop 40. In this position lugs I of sleeve II) have been rotated out of the pathof lugs 8 on barrel I so that barrel I may be quickly withdrawn from receiver I5 and bracket 31 from gas cylinder plug 35 by handle I6. Another barrel is readily inserted within sleeve Ii! and receiver I5 by merely inserting the chamber end of the barrel within sleeve It (handle It should be in the position shown in Fig. 1) and slipping bracket 3| over gas cylinder plug 35 until barrel shoulder II abuts sleeve I0, then lowering handle 11 to the closed position. The headspace of the firearm has been previously adjusted and has not been disturbed so that if the barrels are properly interchangeable further headspace adjustment is not necessary and the firearm is at once ready to fire.

Any firearm embodying this invention cannot be fired with the barrel locking handle I! in the unlocked position for when handle IT is in anything but the fully locked position of Fig. 4 the head d4 of the plunger 42 will be biased into the groove &3 of the operating slide 43 by spring 45. Hence slid 43 cannot be released to load a cartridge While the barrel is unlocked. The dangerous condition thereby eliminated is obvious. Closing handle ll causes arm I9 to bear against the end of plunger 42 and when rotated .to the locked position, head 44 of plunger 42 is forced out of the path of slide 43 against the bias of spring at. The firearm is then ready to load and fire.

After prolonged firing a deposit of carbon invariably forms around the gas port and surrounds the gas cylinder tube plug of any firearm. With most types of firearms it is extremely difiicult to remove the barrel from such a firearm because-of the freezing action due to the carbon deposit encountered at this point. With this invention, however, such freezing is very readily overcome by the camming action produced by the advance of the barrel sleeve II) on the left hand threads 2 when arm I9 is rotated to unlock the barrel from the barrel sleeve and receiver. Such rotation forces the barrel slightly forward from the receiver and in so doing easily breaks the seal between the bracket 3| and gas cylinder tube plug 35 thereby permitting easy withdrawal of barrel I from receiver I5.

From the foregoing description it is apparent that the headspacing feature affords a convenient means for adjusting the headspace of a firearm. The quickly detachable barrel can easily be made to close manufacturing tolerance limits so that each barrel even when made in large quantities, has practically identical measurements and is readily interchangeable, this is especially true with reference to the barrel lugs. Therefore when once the firearm is adjusted for headspace with any one barrel that particular barrel may be rapidly replaced by another without further attention to headspace adjustment of the firearm. In the event it becomes necessary to replace some component of the firearm, such as the bolt forexample, the headspace may be readily adjusted by the headspacing feature previously described. Hence any accumulation of tolerances on the components affecting headspace are readily taken care of by this headspacing feature.

I claim:

1. In a firearm having a barrel and receiver, a plurality of locking lugs disposed around the periphery of the barrel, a locking sleeve having spaced interior lugs corresponding to said looking lugs and arranged to permit the axial insertion of said barrel lugs thru said sleeve in at least one angular position of said barrel with respect to said sleeve, said locking sleeve being threadably mounted to the receiver whereby rotation of said sleeve will vary the longitudinal position of said sleeve with respect to said receiver, an operating member adjacent said sleeve and axially movable with respect to said sleeve, a plurality of serrations on said sleeve, toothed means on said operating member constructed and arranged to en- 7 gage a portion of said plurality of serrations on said sleeve in one axial position of said operating member with respect to said sleeve and to disengage said serrations when said operating memher is axially moved relative to said locking sleeve, means for securing said operating member in said axial position with respect to said sleeve and means for manually reciprocatingly rotating said operating member whereby said sleeve may be rotated between a locking and unlocking position with respect to said barrel.

2. The combination as in claim 1 and means for limiting the reciprocating rotational movement of said operating member to the angular distance between the locked and unlocked rotational positions of said sleeve with respect to the barrel, and means for resiliently securing said sleeve in both the locked and unlocked rotational positions.

3. In a firearm having a barrel and receiver, a plurality of locking lugs disposed around the periphery of the barrel, a locking sleeve having spaced interior lugs corresponding to said locking lugs and arranged to permit the axial insertion of said barrel lugs thru said sleeve in at least one angular position of said barrel with respect to said sleeve, said locking sleeve being threadably mounted to the receiver whereby rotation of said sleeve will vary the longitudinal position of said sleeve with respect to said receiver, an annular recess on the periphery of said sleeve, an operating member surrounding said sleeve in the vicinity of said annular recess and axially movable with respect to said sleeve, screw means in said operating member cooperating with said annular recess to secure said operating member in a fixed axial position with respect to said sleeve,

a plurality of serrations on said sleeve, a toothed portion on said operating member constructed and arranged to engage a portion of said serrations when said operating member is secured by said screw means and to disengage said serrations when said operating member is moved axiall with respect to said sleeve, means for manually reciprocatingly rotating said operating member, means for limiting the reciprocating rotational movement of said operating member to ;he angular distance between the locked and unlocked rotational positions of said sleeve with cespect to the barrel, two spaced groups of serra- ;ions on said operating member, and a spring pressed toothed member on said receiver arranged 1o engage said serrations to resiliently secure said )perating member in either its barrel looking or inlocking rotational positions.

4. In a firearm having a receiver wherein a iarrel receiving locking sleeve is rotatable with espect to the receiver and a barrel axially in- ;ertable through said locking sleeve and arranged ,o be locked to the receiver by rotation of the ocking sleeve, the improvement comprising an )perating member mounted on said sleeve for roatable and axial translative movement with re- :pect to said sleeve, releasable means for securing aid operating member against axial movement '0 a sleeve operating position on said sleeve, and means for connecting said operating member fix- ;dly in angularly adjusted position on said sleeve :1 said secured position whereby said sleeve may re rotated by said operating member, said last mentioned means being constructed and arranged lie in disconnected relation to said operating dember and said sleeve when said operating nember is in a position axially displaced from aid sleeve operating position, whereby the an- 8 gular position of said operating member relative to said sleeve may be selectively adjusted.

5. In a firearm having a barrel and receiver, a plurality of locking lugs fixed on and sp e around the periphery of the barrel, a locking sleeve rotatably screw-mounted coaxially with the barrel on the receiver and having spaced interior lugs corresponding to said locking lugs and arranged to permit the axial insertion of said barrel through said sleeve and passage of the barrel lugs between said lugs of the sleeve to an operating position of the barrel in the receiver in at least one angular position of said barrel with respect to said sleeve, said locking lugs being of a length to lie longitudinally inward of the said lugs on the sleeve at said operating position of the barrel to permit relative rotation of the sleeve, an operating member for said sleeve coaxially rotatable in relation thereto and translatable axially with respect to said sleeve, releasable means for securing said operating member against axial movement in an operating position in relation to said sleeve, and means for connecting said operating member fixedly in angularly adjusted position in relation to said sleeve whereby said sleeve may be rotated by said oper ating member, said last mentioned means being constructed and arranged to disconnect said operating member from said sleeve when said operating member is in a position displaced axially from said operating position whereby the angular position of said operating member relative to said sleeve may be selectively adjusted, said sleeve having an initial position in its rotation whereat it is in unlocked position longitudinally screwed along the barrel axis from locked position, and having its lugs aligned with the spaces between the said locking lugs.

6. In a firearm having a receiver, a locking sleeve rotatable with respect to the receiver and a barrel axially insertable through said locking sleeve and arranged to be locked to the receiver by rotation of the locking sleeve, the improvement comprising an operating member mounted adjacent said sleeve for concentric rotative and axial translative movement with respect to said sleeve, releasable means for securing said operating member against axial movement in a position immediately adjacent said sleeve, a first circumferentially serrated sector on said sleeve and a second serrated sector on said operating member constructed and arranged to intermesh at one axial position of said operating member relative to the sleeve and to clear each other when the operating member is in a position axially displaced from said one position, whereby said sleeve and operating member are releasably secured together and angular position of said operating member relative to said sleeve may be selectively adjusted.

7. In a firearm having a barrel and a receiver, a plurality of locking lugs disposed around the periphery of the barrel, a locking sleeve having spaced interior lugs corresponding to said looking lugs and arranged to permit the axial insertion of said barrel lugs thru said sleeve in at least one angular position of said barrel with respect to said sleeve, said locking sleeve being threadably mounted to the receiver whereby rotation of said sleeve will vary the longitudinal position of said sleeve with respect to said receiver, an operating sleeve surrounding a portion of said locking sleeve, said operating sleeve being mounted for rotatable and axial movement with respect to said sleeve, a removable key in said operating sleeve cooperating with a groove in said locking sleeve to secure said operating sleeve in a fixed axial position relative to said locking sleeve, a first gear-like sector on said locking sleeve, a second gear-like sector on said operating sleeve constructed and arranged to engage said first gear-like sector in said secured position of said operating sleeve, whereby said locking sleeve and operating sleeve are rotatively secured together, and to disengage from said first gear-like sector by axial movement of said operating sleeve from said secured position when said key has been removed from said groove, whereby the angular position of said operating sleeve relative to said locking sleeve may be selectively adjusted.

8. In a firearm having a receiver and a reciprocating operating slide, the improvement comprising a locking sleeve rotatable with respect to the receiver, a barrel axially insertable thru said locking sleeve and arranged to be locked to the receiver by rotation of the locking sleeve, an operating member constructed and arranged to rotate said locking sleeve to its locked position relative to the receiver, and a stop member spring biased into the path of the operating slide, said operating member being constructed and arranged to move said stop member out of the path of the operating slide as said operating member moves to its barrel locking position.

9. In a firearm having a receiver and a reciprocating operating slide, the improvement comprising a locking sleeve rotatable with respect to the receiver, a barrel axially insertable thru 10 said locking sleeve and arranged to be locked to the receiver by rotation of the locking sleeve, an operating sleeve surrounding a portion of said locking sleeve, means for rotatively securing said operating sleeve to said locking sleeve, a handle on said operating sleeve for rotating said operating sleeve and said locking sleeve to the barrel locking position, and a stop member spring biased into the path of the operating slide, said handle having a portion engaging said stop member to move said stop member out of the path of the operating slide as said handle moves to its barrel locking position.

CLARENCE E. SIMPSON.

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

UNITED STATES. PATENTS Number Name Date 499,464 Mason June 13, 1893 605,111 Mason June 7, 1898 618,033 Hemming Jan. 17, 1899 1,234,575 Schneider July 24, 1917 2,115,861 Laloux May 3, 1938 2,121,171 Laloux June 21, 1938 1,363,262 North Dec. 28, 1920 564,043 Benet et a1. July 14, 1896 2,088,268 Lauf July 27, 1937 2,137,612 Higson Nov. 22, 1938 605,734 Mason June 14, 1898

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