WO1995013516A1

WO1995013516A1 - Pressure-regulating composite cartridge with gas expansion zone

Info

Publication number: WO1995013516A1
Application number: PCT/US1993/010511
Authority: WO
Inventors: Marlo K. Vatsvog
Original assignee: AMTECH OVERSEAS Inc
Current assignee: AMTECH OVERSEAS Inc
Priority date: 1993-11-08
Filing date: 1993-11-08
Publication date: 1995-05-18
Anticipated expiration: 1996-05-08
Also published as: AU5589894A

Abstract

A plastic-cased metal-headed ammunition casing for high-powered rifle and cannon cartridges is described in which the plastic case (12) has a pressure regulating baffle (44) or wall in the forward end thereof to regulate and control the development of chamber pressure and directs pressure into a space around the bore of the projectile (10) prior to movement of the projectile. The cartridge is charged with a given charge of powder (38) and the cap or head (14) securely fastened to the rearward portion of the plastic casing. An expandable sleeve (124) may be used to stabilize the head-casing interfit. The head provides sufficient resistance to the residual pressure after firing so that the cartridge can be used in rapid fire automatic weapons.

Description

PRESSURE REGULATING COMPOSITE CARTRIDGE WITH GAS EXPANSION ZONE

BACKGROUND OF THE INVENTION

This invention relates to improvements in the ammunition art, and specifically to improvements in the ammunition of the type used in high power rifles of larger calibers in which an elastomer or plastic is used for a predominant portion of the casing which houses the powder and positions the projectile. The casing is made of a synthetic polymer composition attached to a metallic or elastomeric head positioned at the opposite end of the cartridge from the projectile.

Cartridges of this general type have been known in the literature for many years but have for one reason or another, failed to provide a satisfactory ammunition for sustained automatic fire in the modern automatic larger caliber weapons widely used in police, paramilitary and military situations.

The following patents are known to disclose various types of composite cartridges of the general type to which this invention is addressed:

UNITED STA' IES PATENTS INVENTOR

2,654,319 Roske

2,826,446 Ringdal

3,026,802 Barnet et al.

3,099,958 Daubenspeck, et al.

3,745,924 Scanlon

3,842,739 (unknown)

3,955,506 Luther, et al.

3,874,294 Hale

3,977,326 Anderson

4.147,107 Ringdal

4,738,202 Hebert

5,033,386 Vatsvog

UNITED KINGDOM

1,015,516 Daubenspeck et al. GB2,044,416 Application Hebert

EUROPEAN PATENT APPLICAΗON 0 131 863 (Publn. 23.01.85) Vatsvog

GERMAN PATENT

2,419,881

PATENT COOPERATION TREATY PUBLICATION WO89/07496 Vatsvog

It is recognized that a plastic rifle cartridge should usually have a metal cap or head to carry the primer and to provide the ejection groove necessary to eject the spent cartridge from the firing chamber. When used in a modern automatic weapon the need is also present for a reinforced cap or head area to contain residual pressures in the cartridge occasionally encountered when the ejection cycle begins removal of the cartridge from the chamber before the pressure effects of the recent firing have fully dissipated. To achieve consistent performance, both ballistically and in the operation of the gas operated ejection mechanism, a handgun or rifle cartridge must develop a consistently high chamber pressure level for each round. Heretofore, the attainment of consistent pressure levels has been difficult, due to inconsistencies in the interfit between the bullet and the cartridge, improper sizing of the powder chamber for the powder used, and to the many variations in the performance in the burning cycle of the various powders available for use in rifle ammunition.

Several attempts have been made to develop a reusable handgun casing made of lightweight plastic materials, including my successful development described in my European Patent Application No. 0 131 863. In the use of plastic casings of the prior art, it is necessary that there be a tight fit between the casing and the bullet and between the casing and the head in order to prevent the escape of the gases formed when the powder charge is ignited. These gases in the handgun loads can quickly reach a pressure of over 10,000 psi, and thus the seal around the bullet and around the head must be tight enough to prevent escape of the gases until the bullet is discharged. In rifle applications, such as the NATO 5.56 mm

(.223 caliber) widely used in weapons such as the M-14 and M-15 used by the United States of America and its allies and various 5.56 mm rifles used by other military forces, pressures of 40,000 to 60,000 psi or higher may be encountered. The seal around the head is of extreme importance at these higher pressures as well as the strength of the head extending along a substantial distance of the side wall of the cartridge to prevent rupture of the

sidewall of the cartridge during ejection of the spent cartridge. Such a rupture and escape of the gases could not only adversely effect the performance of the bullet being discharged but could also potentially adversely affect the subsequent firing of the rifle and could present a safety hazard to the rifleman or his companions.

Of great significance is the need to controllably maintain the chamber pressure developed by detonation or burning of the powder during the firing cycle so that a consistent pressure level is attained for a given powder load and type. Also of importance, particularly in the instance of handgun and larger caliber projectiles, is the need to evenly distribute the pressure around the outside of the circumference of the projectile before the motion of the projectile is initiated so that the thin area of the cartridge is forced circumferentially outwardly into firm contact with the chamber of the weapon so that the thin portion of the cartridge holding the projectile is not damaged during the firing cycle. In brass cased ammunition the pressure level is attained during and following burning of the powder in

part through the crimp or frictional interfit between the bullet and the inner wall of the case. With plastic cases the control of the pressures has heretofore been erratic and unacceptable. For military rounds, the need for reloading capability is minimized, so long as the round is relatively inexpensive to manufacture and load, and so long as the other desirable factors of the cartridge, such as corrosion resistance, weight, moisture resistance and the like provide a cartridge as dependable as brass.

Brass cartridges rely upon the crimp or frictional engagement with the bullet to control the buildup of pressure before bullet ejection. A more consistent and reliable control would provide more nearly consistent ballistics performance and is one of the attributes of this invention.

In all of the patents mentioned above the cartridge is formed of a composite plastic or metal and plastic casings which rely on multiple parts to provide the sealing around the end caps or head, and require a crimp about the bullet to hold the bullet in place. The cost of producing and assembling a multiple piece casing is high and heretofore the composite casings have not accomplished the dual functions of sealing the head to the plastic casing and the plastic casing to the bullet in a manner which permits the resulting cartridge to be used in fully automatic rifle firing applications. In large diameter rounds, the prior art devices have not provided for a configuration of the cartridge which will adequately withstand the forces upon the cartridge to prevent its damage during the firing cycle, frequently resulting in portions of the cartridge becoming separated form the rest of the cartridge during the firing cycle and becoming lodged in the chamber of the gun, thence causing a misfire or jam of the next round.

DISCLOSURE OF THE INVENTION It is an object of this invention to provide a lightweight plastic composite cartridge for use in high velocity rifle applications in which the pressure developed by ignition of the powder is controlled.

It is another object of the invention to provide a cartridge for rifle ammunition which can be used in fully automatic weapons.

Another object of this invention is to provide a cartridge which has a frangible pressure

control bulkhead or partition which imparts pressure and force against the base of the bullet after a threshold level of pressure is attained to assure optimum powder ignition and complete burning.

A still further object of this invention is to provide ammunition in a cartridge in which the bullet can be inserted or removed easily without exposing the powder.

One further object of this invention is to provide a cartridge for rifle use which can have its powder load inserted from the base or head end of the cartridge without the presence of the bullet.

Another object of this invention is to provide a cartridge for use in a rifle which has a light frictional interfit with its bullet and no crimp or its equivalent to hold the bullet in place, for smooth and reproducible ejection of the bullet from the cartridge upon firing.

One specific object of this invention is to provide a large caliber round which has improved pressure distribution at the base of the projectile so that the projectile receiving portion of the casing is undamaged during the firing cycle.

These and other objects of this invention are obtained by providing a tubular plastic casing made of a durable but elastic plastic material such as nylon which has the structural integrity to remain intact around the area upon which a metallic head is mounted or a malleable skirt is swaged to form the interconnection between the plastic casing and the head. The casing is formed by injection molding a relatively simple shape which may have draft angles built in to permit easy removal of the part from the male mold part. In the process of molding a partition or pressure control septum is molded in at the bullet-receiving end of the casing to define a bullet receiving recess and a powder receiving recess. A metal head is formed to slip on the end of the casing opposite the bullet receiving recess and interfit with or be swaged into faired contact with the periphery of the casing in a sealed joint. Alternately, the head may be formed or swaged prior to assembly and the elastomer casing forced into the head, the elastomer material being yieldable but possessing plastic memory sufficient to urge it toward its original shape and into firm contact with the interior surface of the head. Advantageously, the head may be provided with interior ridges or recesses which mate with corresponding ridges and recesses formed on the periphery of the plastic case. An interior expansion sleeve may also be provided to distribute the pressure of the powder ignition evenly around the entire area of the plastic metal interface while firmly capturing the plastic between the head and the expansion sleeve. The head has a primer recess into which a primer may be inserted coaxially with the head and casing. A primer flash hole or central vent extends coaxially into the powder chamber to ignite the powder upon detonation of the primer. The powder chamber is defined by the plastic casing, the pressure regulating frangible partition and by the head when it has been inserted axially over the casing and the skirt or a part thereof swaged into a fared interlock with the casing or forced into interlocking circumferential grooves and ridges. The volume of the powder chamber may be varied according to the type of powder being used so that the powder used fills the chamber to simplify loading and to optimize the burning characteristics of the powder. The pressure regulating front partition preferably is thickened from the frangible annular periphery thereof toward the cartridge axis with an annular frangible zone configured to control the pressure buildup in the cartridge but provide a certain location for separation from the cartridge wall without damage thereto. The bullet recess provides a pressurization zone for application of pressure outwardly to the casing surrounding the

projectile before the projectile motion is initiated, so that the plastic in the area of the projectile is forced outwardly into tight contact with the chamber of the gun, thus helping to insure that the plastic will not be torn apart by the departing projectile. The frangible partition functions to separate the powder chamber from the bullet receptacle, to seal the powder chamber at the forward end thereof and to provide a controlled pressure rupture threshold to controllably regulate the generation of pressure during the firing cycle so that the power of the powder is both maximized and controlled by regulating the pressure level at which the projectile begins to move. The strength of the frangible annulus is tailored to the powder type and charge to provide the optimum powder burn cycle by increasing or decreasing the thickness during molding and by choice of the elastomer used.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an exploded perspective view of the composite cartridge of this invention for use with a boat tail bullet.

Fig. 2 shows one embodiment of this invention with the casing and head in cross section. Fig. 3 is a partial cross sectional view of a second embodiment of the cartridge of this invention for use with a flat base bullet.

Fig. 4 is a cross sectional representation of the head area of another embodiment of this invention.

Fig. 5 is an axial cross section of another embodiment of the cartridge of this invention showing a modified form of the pressure regulating frangible partition.

Fig. 6 is a cross sectional view taken along lines 6-6 of Fig. 4.

Fig. 7 is a further embodiment of the front area of the cartridge of this invention wherein gas produced by the burning of the powder is permitted to escape between the projectile and the case thereby forcing the case outwardly into firm contact with the side-wall of the chamber, thereby stabilizing the case until the projectile exits the case.

DETAILED DESCRIPTION

AND BEST MODE FOR CARRYING OUT THE INVENTION

Referring particularly to the drawings wherein like figures indicate like parts, there is seen in Fig. 1 an exploded view of one embodiment of this invention. A rifle cartridge suitable for use with high velocity rifles is shown manufactured with a polymer case 12 and a metallic head 14. A bullet 10 having a circumferential groove 60 is shown positioned for insertion into the forward end of plastic casing 12. A pressure regulating front partition 44

(best seen in Figs. 2 through 6) securely closes off the forward portion of outer chamber 36 and is adapted to receive the base 61 of bullet 10. The forward portion of casing 12 has a thickened shoulder 42 forming chamber taper 40. The shoulder 42 supports a frangible annular zone 48 which is engineered and designed to be severed cleanly completely around the periphery of the shoulder 42 when sufficient pressure is developed on the interior of powder chamber 36. The pressure regulating front partition 44 has a semi spherical surface 46 projecting rearwardly into the powder chamber 36 to aid in the even distribution of pressure to the bullet 10 upon detonation of the powder charge 38 contained in chamber 36. The frangible annulus 48 is sized in thickness to provide the desired level of pressure before bursting so that a controlled powder detonation can occur and further to provide the

more nearly controllable pressure application to the base of bullet 10. The presence of the pressure regulating front partition 44 is made possible by the composite configuration of the cartridge. The front partition 44 is molded as a part of and extends inwardly from shoulder 42. The interior volume of powder chamber 36 may be varied to provide the volume necessary for complete filling of the chamber 36 by the powder chosen so that a simplified volumetric measure of powder can be utilized when loading the cartridge.

The end of plastic casing 12 opposite from the pressure regulating front partition 44 has means to engage and seal to a metallic head 14. Casing 12 is formed with a tapered skirt interlock surface 30 adapted to mate with and interlock with the deformable skirt 20 of head 14. The skirt interlock surface 30 preferably tapers from a larger diameter at the rearward most portion 64 thereof to a smaller diameter at the forward portion 65. A swaging anvil 22 may be used to provide backing for swaging of head 14 onto plastic casing 12. Anvil 22 is received within anvil recess 32 and provides support for the plastic casing 12 during the swaging process. Chamfers 24 are provided for ease of insertion of the anvil into the casing.

Head 14 is formed in a high pressure head forming apparatus as is well known in the prior art. However, the die used provides for a diverging deformable skirt 20 having a larger diameter at the skirt tip 54 and a relatively smaller diameter, approximating the outside diameter of head 14 at the skirt base 56. The thickness of skirt 20 increases from skirt base 56 to skirt tip 54 so that when swaged into contact with the tapered skirt interlock surface 30 a faired substantially cylindrical surface along the entire length of the assembled cartridge will result with a physical interlock between head 14 and plastic casing 12. Head 14 also has an extraction groove 26 cut therein and a primer recess 18 formed therein with primer chamfer 29 for ease of insertion of the primer 16. The primer recess 18 is sized so as to receive the primer 16 in an interference fit during assembly. A primer flash hole 28 communicates through the anvil central vent 34 into the powder chamber 36 so that upon detonation of primer 16 the powder in powder chamber 36 will be ignited. An alternative structure would include a groove at portion 65 to receive a swaged tip section 54 in a head configuration without the flared skirt configuration described above.

Bullet 10 is held in place within bullet recess 50 by a frictional interfit. The bullet may be inserted into place following the completion of the filling of powder chamber 36 and final assembly of the cartridge by swaging the deformable skirt 20 into contact with the tapered skirt interlock surface 30. In this way bullets of differing size and characteristics can be utilized and may even be interchanged without affecting or exposing the powder in powder chamber 36.

Whenever a flat bottom bullet is used the configuration shown in Fig. 3 may be used to accommodate the particular bullet shape desired. In this embodiment the shoulder 42' is formed with a smaller interior angle from the axis to accommodate the full diameter of bullet 11'. The flat base 61' rests against the pressure regulating front partition 44' which is configured with a larger diameter so that the entire base 61' receives the pressure developed within chamber 36'.

Further embodiments in variant forms useful particularly for large caliber cartridges such as 50 caliber cannon rounds and the like are shown in Figs. 4-7. It has been discovered that a critical feature of successful large caliber rounds is the provision of a means to stabilize the case against the chamber in the area of the projectile before the projectile begins its movement into the barrel from the chamber. Stabilization of the sidewall is also of

importance in handgun rounds. This stabilization is necessary to prevent localized failure of the case wall adjacent the projectile and is accomplished by pressurizing the space around the base of the projectile before the projectile begins its motion. A space 174 is formed by the interior wall 176 of the bullet receiving recess at the forward portion of casing 112, the forward surface 179 of partition 146 or 146,' and the rearward surfaces of the boattail portion of the projectile 110. The rapid buildup of pressures in space 174 after rupture of the partition 146 or 146' and before movement of projectile 110 causes stabilization of the case against the chamber by forcing the case outwardly into supporting contact with the side wall of the cartridge chamber. The result is a stabilization effect on the case prior to the time the projectile exits the case. Figures 5 and 7 also show the forward portion of case 112 being molded into canalure 160 as a means to hold projectile 110 in place and further control the buildup of pressure before movement of the projectile 110 begins. The thickness and strength of the plastic material at canalure 160 is engineered to provide the desired pressure buildup in the chamber from the burning of the powder. The combination of the forces needed to initiate movement due to the canalure-cartridge interengagementand the pressures initially needed to fracture the frangible wall 146 or 146' in FIGS. 5 and 7 controls the pressure buildup within the chamber of the case 112. The fracture zone 148 controls the location at which the front partition 146 and 146' separates from thickened portion 150 of case 112 and the configurations shown in FIGS. 5 and 7 permit the rapid pressure buildup in space 174. It has been found that the case stabilization described above is advantageous to prevent separation of the case at the shoulder 150.

Shown also in FIGS. 5 and 7 are longitudinal ribs 101 which extend along the length of the case to provide additional stability to the case and to form seats 102 as shown in FIG. 6.

Two different embodiments of the front partition 146 and 146' are shown in FIGS. 5 and

7. Both embodiments utilize a thin frangible area 148 at the periphery of the disk-like pressure regulating partition 146 and 146' designed and engineered to fracture at a predetermined level of pressure within the propellant chamber of the devices shown at

FIGS 5 and 7. The propellant 109 is typically a relatively slow burning powder such as is widely used in high velocity rifles.

In FIGS. 4 and 5 a configuration of the head and casing is shown which is particularly adapted to large caliber rounds. Case 112 has longitudinal ribs 101 extending along a part of the length of the interior of the shell case and terminating at sleeve support surfaces 102 and interior sleeve 124 is shown positioned with the full diameter portion 123 thereof resting upon the surfaces 102 and engaging the inner surface of case 112. The smaller diameter portion 122 of expansion sleeve 124 is shown spaced inwardly from the inner surface of plastic casing 112. The space between reduced diameter section 122 and the inner surface of the cartridge permits the plastic of the cartridge to be deformed inwardly during assembly with cap 156. Cap 156 is shown with interiorly disposed ribs 180 which are intended to mate with grooves 111 formed in plastic casing 112. The interfit of the grooves and recesses all as shown in FIG. 4 provides a secure attachment of the head to the case. The purpose of expansion sleeve 124 is to stabilize the head-case interface upon ignition of the propellant 109. As pressure increases within the cartridge case the small diameter portion 122 of expansion sleeve 124 expands outwardly into contact with the inner surface of plastic casing 112 which thereby forces it into secure engagement with the grooved and ridged portion of head 156. Further outward expansion of the assembly causes the head and cartridge to come into supporting engagement with the chamber of the rifle of canon. Having expanded into firm contact with case 112 the previously reduced diameter portion 122 of expansion sleeve 124 provides secure support for the mechanical interlock between

the case and the head for automatic ejection of the cartridge case after firing.

For clarity FIG. 6 is a cross-sectional view taken along lines 6-6 of FIG. 4 and shows the expansion sleeve support surfaces 102 on ribs 101.

The experienced handloader or ammunition manufacturer will know that many powder types and weights can be used to prepare workable ammunition and that such loads may be determined by a careful trial including initial low quantity loading of a given powder and the well known stepwise increasing of a given powder loading until a maximum acceptable load is achieved. Extreme care and caution is advised in evaluating new loads. The powders available have various burn rates and must be carefully chosen so that a safe load is devised. The foDowing examples show some of the stepwise progression of loads undertaken by the inventor to establish the acceptable chamber pressures, bullet velocities and performance at this inventor's present stage of development which reflect workable and usable ammunition.

I claim as my invention:

Claims

1. A cartridge for use in a rifle or the like having a cartridge receiving chamber, said cartridge comprising a head interfitted with a plastic casing, said casing having a bullet end and a head end, said bullet end having a bullet receiving recess adapted to receive a bullet in a frictional engagement and having a pressure regulating front partition separating said bullet recess from a powder chamber, said pressure regulating front partition being molded integrally with said casing and having a frangible annulus whereby said partition resists removal thereof until a predetermined pressure is achieved in said chamber by an ignited propellant charge, said casing further providing a space between said partition and said bullet whereby, upon propellant ignition and separation of the partition, said space is pressurized before movement of the projectile begins to stabilize said casing adjacent to said space against said chamber; an external interlock surface at said head end, a cartridge head having a casing engaging recess at one end thereof and a primer receiving recess in the other end thereof, said casing engaging recess receiving said casing therein and extending toward said bullet receiving end around the outside of said external interlock surface and fairing with said casing.

2. The cartridge of claim 1 wherein said external interlock surface comprises a circumferentially ridged surface adapted to interengage and mate with interior grooves on said head.

3. The cartridge of claim 1 wherein the casing is molded with longitudinally positioned ribs on the interior of the casing extending along at least a portion of the interior of the casing.

4. The cartridge of claim 3 wherein said ribs form expansion sleeve supporting and locating surfaces nearby said interlock surfaces.

5. The cartridge of claim 1 wherein the interior volume of said casing is sized to permit entry of a chosen powder sufficient to provide from 40,000 to 60,000 psi chamber pressure upon firing in a rifle chamber.

6. The cartridge of claim 1 wherein said pressure regulating front partition has on its rearward face a semicylindrical surface.

7. The apparatus of claim 1 wherein an expansion sleeve is inserted into said cartridge at said interface between said cartridge and said head to support said interface against said chamber during firing.

8. A method of manufacturing a rifle cartridge comprising the steps of: molding a substantially cylindrical plastic cartridge casing having a bullet receiving end and a head receiving end, said bullet receiving end having a bullet recess to receive a bullet and having a pressure regulating front partition at the base of the bullet recess extending across the casing separating the bullet recess from a powder chamber, said bullet recess formed to hold the bullet at a spaced apart relationship with said partition so that an open space is present at the base of said projectile, whereby upon ignition of the propellant in said case, said partition fractures and pressurizes said open space before said projectile moves, and said head receiving end having a circumfrential head interlock surface thereon; forming a cartridge head having a coaxial primer recess and a coaxial casing receiving recess, said casing receiving recess having interior grooves and ridges adapted to interfit with complementary ridges and grooves on the exterior of said casing; placing a charge of propellant in said casing, and; assembling said casing and said head.

9. The process of claim 11 further including the steps of: placing a deformable expansion sleeve into said cartridge; inserting a bullet into said bullet recess; and forming a portion of the bullet recess into a canalure on said bullet so that said bullet is locked in place.

10. The method of claim 11 and interlocking said head and said casing to prevent relative rotation.

11. The method of claim 13 wherein said head and said casing are interlocked mechanically.

12. The method of claim 13 wherein said head and said casing are adhesively bonded together.

13. The method of claim 13 and sizing said casing to receive a predetermined volume of powder.

14. The method of claim 11 and sizing said pressure regulating front partition to sever at a predetermined chamber pressure.

15. In a cartridge for use in a rifle or the like having a cartridge receiving chamber, said cartridge comprising a head interfitted with a plastic casing, said casing having a bullet end and a head end, said bullet end having a bullet receiving recess adapted to receive a bullet in a frictional engagement and having a pressure regulating front partition separating said bullet recess from a powder chamber, said pressure regulating front partition being molded integrally with said casing and having a frangible annulus whereby said partition resists removal thereof until a predetermined pressure is achieved in said chamber by an ignited propellant charge, the improvement wherein said casing further providing a

space between said partition and said bullet whereby, upon propellant ignition and separation of the partition, said space is pressurized before movement of the projectile begins to stabilize said casing adjacent to said space against said chamber.

16. The cartridge of claim 15 wherein the casing is molded with longitudinally positioned ribs on the interior of the casing extending along at least a portion of the interior of the casing.

17. The cartridge of claim 15 wherein said pressure regulating front partition has on its rearward face a semicylindrical surface.