US3771452A - Reinforcing movable head for protection against ruptured cartridge cases - Google Patents

Abstract

In order to improve the obturation capability of firearm cartridges fabricated from materials other than brass, the usual enlarged extraction rim at the rear end thereof is replaced by a ring fabricated from a more deformable material than the case and provided with a beveled forward portion arranged to be expanded into obturating contact with the interior of the firing chamber in response to the forward movement of the bolt into battery position. The ring also includes an exterior groove engageable with the extractor carried by the bolt and an interior groove into which the firing pressures will swage the material of the cartridge case to provide sufficient locking engagement therebetween to withstand the extraction forces imparted thereto by the extractor during the recoil travel of the bolt.

Description

United States Patent 1 1 3,771,452 Reed et al. Nov. 13, 1973 i 1 REINFORCING MOVABLE HEAD FOR FOR I NP EN S R PPLC TI NS PROTECTION AGAINST RUPTURED E G AT T O A I A O CARTRIDGE CASES 213,678 9/1909 Germany 102/44 [75] Inventors: Frederick P. Reed, Davenport, Iowa; Primary Examiner-Robert F. Stahl J. Phillip Langdon, Moline, Ill. Attorney-Harry M. Saragovitz et :al. [73] Assignee: The United States of America as represented by the Secretary of the t [57] ABSTRACT Army, Washington, DC. In order to improve the obturatioln capability of firev arm cartridges fabricated from materials other than [22] Flled' 1972 brass, the usual enlarged extraction rim at the rear end [2]] Appl. No.: 242,057 thereof is replaced by a ring fabricated from a more deformable material than the case and provided with a beveled forward portion arranged to be expanded into 02/43 421; obturating contact with the interior of the firing cham- [58] Fie'ld 40 43 R ber in response to the forward movement of the bolt into battery position. The ring also includes an exte- 102/43 89/26 rior groove engageable with the extractor carried by [56] References Cited the bolt and an interior groove into whlch the firing pressures Will swage the material of the cartridge case UNITED STATES PATENTS to provide sufficient locking engagement therebe- 3,690,256 9/1972 Schnitzer 102/44 tween to withstand the extraction forces imparted 2,654,319 10/953 Roske 102#13 P thereto by the extractor during the recoil travel of the 3,026,802 3/1962 Barnet et al. 102/44 x bolt 3,675,576 7/1972 Whitney .r 102/44 2,823,611 2/1958 Thayer 102/44 4 Claims, 4 Drawing Figures REINFORCING MOVABLE HEAD FOR PROTECTION AGAINST RUPTURED CARTRIDGE CASES BACKGROUND OF THE INVENTION This invention relates to firearm cartridges fabricated from materials of less deforrnability than brass and is more particularly directed to means for improving the obturation between the cartridge case and the firing chamber to prevent rearward escape of the gases generated during firing especially in the event of a rupture, break, or leak in the case.

While the case portions of military firearm cartridges are usually fabricated of brass in order to provide the strength and deforrnability required to insure rapid obturation of the firing chamber in the firearm against the rearwardescape of the discharge gases, the increasing scarcity and cost of copper has prompted numerous attempts to utilize molded organic plastics, aluminum, or even steel as a substitute material. These attempts have met with some degree of success in firearms designed for commercial and sporting use but have not been acceptable where the cartridges have been of the high pressure type required for military firearms which are operated at high rates of sustained fire. The major drawback of these lighter and less costly materials has been their inability to expand with sufficient rapidity into full obturating contact with the interior of the firing chamber in the firearm. Furthermore, where the need for a substantial reduction in the weight of the cartridges has dictated the fabrication of the case portions thereof from a lightweight material such as aluminum, it has been found that the feeding of a belt of linked cartridges into the firearm and the subsequent delinking of each cartridge prior to the chambering thereof frequently produces nicks and scratches thereon of considerable depth relative to the wall thickness of the case itself. In view of the relatively thin walls required of aluminum cases in order to maximize the rapidity of the obturating expansion thereof in response to the firing pressures, any imperfections or reductions reaches the wall thickness introduces the possibility of actual ruptures or breaks prior to the completion of firing. Obviously, any failure to fully obturate the firing chamber against the extremely hot and corrosive gases generated during firing could lead to catastrophic fail ure of the firearm as well as severe injury to the operator thereof.

SUMMARY OF THE INVENTION It has been found that the foregoing difficulties can be eliminated by modifying a conventional cartridge case of aluminum or other lightweight material to omit the annular flange customarily utilized to form the rear wall of the extractor groove and utilizing the remaining cylindrical portion to seat an obturating ring of a more deformable material than that employed in the case. The forward end of such ring is interiorly beveled at a steeper angle than the inclined annular shoulder extending forwardly from the cylindrical rear end portion of the cartridge case. Thus, as the firearm bolt is advanced into position to close the breech, it forces the ring forwardly causing the beveled portion thereof to ride up the annular shoulder on the cartridge case and be diametrically expanded into obturating contact with the interior surface of the firing chamber. This initial expansion of the ring is thereafter increased by the setback imparted to the cartridge case during firing to more effectively seal the gap ordinarily left between the front face of the firearm bolt and the rear face of the barrel after the former reacher battery position.

The obturating ring is also provided with an extracter groove in the exterior periphery thereof to permit the customary withdrawal of the fired cartridge case from the firearm barrel during the opening of the breech. In order to prevent separation between the obturating ring and the cylindrical rear end portion of the fired cartridge case during extraction, the interior of the ring is formed with a shallow annular groove arranged to receive the metal which is swaged or otherwise forced therein in response to the extremely high firing pressures exerted against the relatively thin cross-section surrounding the primer cavity. In addition to the locking. function thereof, the ring also seals against the rearward leakage of any discharge gases in the event a rupture or break in the cartridge case permits a hypervelocity gas flow between the inclined mating surfaces on the ring and on the shoulder of the case.

It is therefore an object of this invention to provide an improved firearm cartridge wherein the rear end of the case portion thereof is provided with a separate obturating ring for sealing the firing chamber against the potential rearward escape of the discharge gases.

Another object of this invention; is to provide a cartridge case with an obturating ring which will be advanced into initial sealing contact with the interior of the firing chamber in the firearm barrel during the closure of the breech.

Still another object of the present invention resides in the provision of a firearm cartridge, as aforesaid, which will fully obturate the firing chamber therefor even in the event of a rupture or break in the walls of the cartridge case prior to the completion of the firing expansion thereof.

An additional object of this invention is to provide a obturating ring, as aforesaid, which will also serve to transfer the breech opening movement of the firearm bolt to the fired cartridge case in order to effect the extraction thereof from the firing chamber.

BRIEF DESCRIPTION OF THE DRAWING The exact nature of the invention, as well as other objects and advantages thereof, will be readily apparent from consideration of the following specifications relating to the annexed drawing wherein:

FIG. 1 is a central longitudinal section of portions of a firearm breech and bolt and includes a cartridge provided with the obturating ring of the present invention, the parts being shown immediately prior to the completion of the forward travel of the bolt into battery position;

FIG. 2 is a view similar to that of FIG. 1 but showing the initial obturating position imparted to the ring at the conclusion of the closure of the breech;

FIG. 3 is a view similar to that of FIGS. 1 and 2 but showing the position of the obturating ring during the firing of the cartridge; and

FIG. 4 is a perspective view of the obturating ring partly broken away to show the interior and exterior configuration thereof.

DESCRIPTION OF A PREFERRED EMBODIMENT As shown in the drawing, the present invention is particularly applicable to military cartridges I2 of the type which are rammed into afiring chamber 14 in the breech end of afirearm barrel 16 by a forwardly movingbolt 18 provided with a cartridge seating recess 20 in the front face thereof. While such cartridges l2 customarily terminate in a flanged rim at the rear end of thecase portion 22 which cooperates with an inclinedannular shoulder 24 spaced forwardly thereof to define an extractor groove, for this invention the rim is eliminated thereby leavingcase portion 22 with a cylindricalrear end 26 containing thecavity 28 required to house the cartridge primer 30. Although aluminum or an alloy thereof is preferably selected as a substitute material for the standard brass,cartridges 12 may also be fabricated from steel or a high strength molded organic plastic.

In order to improve the obturation offiring chamber 14 during the discharge ofcartridge 12, aring 32 of a more deformable material than the material of thecartridge case 22 is press-fitted onto the cylindricalrear end 26 thereof into contact withannular shoulder 24 thereon. Although not necessarily-limited thereto,ring 32 is preferably fabricated of a hardened copper or of brass with a high copper content to insure maximum deformability while still retaining some degree of strength for a purpose to be explained. The forward portion of obturatingring 32 is interiorly beveled, as indicated at 34, to provide a forwardly decreasing cross-section terminating in acircular knife edge 36, The angle ofbevel 34 is steeper than that ofannular shoulder 24 oncartridge case 22 and consequently leaves aspace 38 therebetween of triangular configuration as best shown in FIG. 1. The portion ofring 32 extending rearwardly ofbevel 34 is of uniform diameter and of sufficient length to project beyondcase 22 to an extent at least equivalent to the dimension of the base oftriangular space 38.

The press-fit betweenring 32 andcylindrical end 26 ofcase 22 is sufiiciently tight to prevent dislodgrnent ofring 32 by the forces normally encountered during the feeding ofcartridges 12 into the firearm and the subsequent delinking operation required to free each cartridge for insertion intofiring chamber 14. However, once the forward travel ofcartridge 12 intofiring chamber 14 is completed, the continued movement ofbolt 18 into locked battery position forces obturatingring 32 forwardly thereby causingbeveled portion 34 to move into mating contact withannular shoulder 24. As a result,beveled portion 34 is diametrically expanded as best shown at 39 in FIG. 2, into obturating contact with the interior wall surface offiring chamber 14 along a distance depending on existing tolerances and the degree of deformability ofring 32. This initial obturation of firing chamber 15 serves to momentarily delay the flow of any discharge gases around the exterior ofcartridge case 22 until the firing pressures reach the level required to complete the set-back normally encountered during the beginning of the firing cycle.

Once such set-back ofcartridge case 12 is completed, the extent of the obturating contact betweenring 32 and the interior surface offiring chamber 14 will be appreciably increased, as best shown in FIG. 3, thereby insuring positive sealing of thegap 40 ordinarily present between the rear face ofbarrel 16 and the front face ofbolt 18 especially after the firing setback ofcartridge 12 has been completed. Thus, even ifcartridge case 22 should rupture or break prior to completion of the firing expansion thereof infiring chamber 14, the required obturation thereof will be effectively accomplished byring 32. Inasmuch asring 32 andcase 22 are fabricated of different materials, the propagation of any cracks or ruptures in the latter will be effectively halted at the mating surfaces therebetween.

In order to provide for the subsequent extraction of the firedcartridge case 22 during the recoil movement ofbolt 18, anextractor groove 42 of conventional configuration is provided in the exterior periphery of obturatingring 32. In addition, the interior periphery ofring 32 includes a relativelyshallow groove 44 preferably in vertical alignment withextractor groove 42. Ascartridge 12 is fired, the rising pressure therein acts on the walls ofprimer cavity 28 to actually swage the material thereof intogroove 44 in the interior wall surface of obturatingring 32 as indicated at 46 in FIG. 3 thereby effectively locking such ring tocartridge case 22. Thus,ring 32 provides thegroove 42 required to receive the forward end of an extractor (not shown) onbolt 18 so that the recoil travel thereof will effect the withdrawal of the firedcase 22 fromfiring chamber 14 inbarrel 16.

In addition to the locking function thereof, the material swaged intogroove 44 of obturatingring 32 also serves to seal against the flow of any of the discharge gases between the inclined mating surfaces ofannular shoulder 24 andbeveled portion 34 which has been found to take place in the event of any rupture or break incase 22 prior to completion of the firing expansion thereof infiring chamber 14.

Thus, there is here provided a simple yet positive means for effectively obturating the firing chamber against the rearward escape of the discharge gases ordinarily encountered during the firing of an aluminum cartridge therein in the event the case thereof cracks or ruptures prior to completion of the firing expansion thereof.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

We claim:

1 A cartridge for a firearm having a barrel cooperating with a reciprocal bolt in the battery position thereof to complete a split firing chamber, said cartridge comprising,

a case having a rearwardly facing beveled shoulder and a cylindrical portion of reduced diameter extending rearwardly from said shoulder, and

an obturating ring of a more deformable material than said case seated on said cylindrical portion and having a beveled front end concentric with said beveled shoulder and sloped to form a triangular space therebetween, said ring being equal in diameter to said case and of sufficient length to project rearwardly beyond said cylindrical portion into the path of the bolt during the movement thereof into battery position whereby said ring is initially deformed into obturating contact with said beveled shoulder and with the interior surface of the barrel and is thereafter additionally deformed during the firing of the cartridge to fully bridge the gap created between the bolt and the barrel by the rearward setback imparted to the bolt upon firing.

2. The cartridge defined in claim 1 wherein said case is fabricated of aluminum and said obturating ring is fabricated of brass.

3. The cartridge defined in claim 1 including means responsive to the forces generated during the firing of the cartridge for locking said obturating ring to said cylindrical portion of said case to permit the subsequent extraction thereof from the firing chamber during movement of the bolt out of battery position.

4. In a firearm having a barrel and a bolt arranged for reciprocal movement into and out of battery position relative to the barrel, the bolt having cylindrical recess in the front end thereof cooperating with the breech end of the barrel to form a split firing chamber for a cartridge provided with a rearwardly facing beveled shoulder and a cylindrical primer housing of reduced diameter projecting centrally rearward of the beveled shoulder, the improvement of means for obturating the gap produced between the bolt and the barrel by the setback forces encountered during the firing of the cartridge, said means comprising,

an obturating ring of a more deformable material than the cartridge seated on the primer housing to extend rearwardly beyond the rear end thereof and forwardly beyond the split between the bolt and the barrel,

a beveled surface on the front face of said ring concentric with said beveled shouider of the cartridge and sloped to form a triangular space therebetween whereby the forward movement of the bolt into battery position deforms said ring into obturating contact with the beveled shoulder of the cartridge and with the interior wall surface of the barrel and whereby the subsequent firing of the cartridge additionally deforms said ring into obturating contact with the interior surface of the cylindrical recess in the front end of the bolt rearwardly of the split in the firing chamber, and

means responsive to the forces generated during the firing of the cartridge for locking said obturating ring to the cylindrical primer housing to permit the subsequent extraction of the cartridge from the firing chamber during the rearward movement of the bolt out of battery position.

Claims (3)

1. 2. The cartridge defined in claim 1 wherein said case is fabricated of aluminum and said obturating ring is fabricated of brass.
2. 3. The cartridge defined in claim 1 including means responsive to the forces generated during the firing of the cartridge for locking said obturating ring to said cylindrical portion of said case to permit the subsequent extraction thereof from the firing chamber during movement of the bolt out of battery position.
3. 4. In a firearm having a barrel and a bolt arranged for reciprocal movement into and out of battery position relative to the barrel, the bolt having cylindrical recess in the front end thereof cooperating with the breech end of the barrel to form a split firing chamber for a cartridge provided with a rearwardly facing beveled shoulder and a cylindrical primer housing of reduced diameter projecting centrally rearward of the beveled shoulder, the improvement of means for obturating the gap produced between the bolt and the barrel by the setback forces encountered during the firing of the cartridge, said means comprising, an obturating ring of a more deformable material Than the cartridge seated on the primer housing to extend rearwardly beyond the rear end thereof and forwardly beyond the split between the bolt and the barrel, a beveled surface on the front face of said ring concentric with said beveled shoulder of the cartridge and sloped to form a triangular space therebetween whereby the forward movement of the bolt into battery position deforms said ring into obturating contact with the beveled shoulder of the cartridge and with the interior wall surface of the barrel and whereby the subsequent firing of the cartridge additionally deforms said ring into obturating contact with the interior surface of the cylindrical recess in the front end of the bolt rearwardly of the split in the firing chamber, and means responsive to the forces generated during the firing of the cartridge for locking said obturating ring to the cylindrical primer housing to permit the subsequent extraction of the cartridge from the firing chamber during the rearward movement of the bolt out of battery position.

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