WO1999040387A1

WO1999040387A1 - Cartridge case

Info

Publication number: WO1999040387A1
Application number: PCT/US1999/002200
Authority: WO
Inventors: James W. Pickett; George C. Mei
Original assignee: Olin Corporation
Priority date: 1998-02-05
Filing date: 1999-02-02
Publication date: 1999-08-12
Also published as: AU2574899A

Abstract

A cartridge (20) case (22) includes a wall (30) extending from a fore end (32) to an aft end (34). A mouth is defined at the fore end and configured to receive a bullet (24). A head (36) at the aft end has a front surface (38) and an aft surface (40). The front surface and wall define a cavity configured to receive a propellant (26). The head has surfaces (44, 46) defining a primer pocket extending forward from the aft surface and has a surface (48) defining a flash venting (49) extending from the primer pocket to the cavity. The primer pocket is configured to receive a primer (28). The primer pocket has a generally cylindrical surface portion (44) configured for engaging the primer. The flash venting has an enhanced minimum cross-sectional area to reduce the recoil of lead-free primers. In one embodiment, the cylindrical surface portion of the primer pocket is no greater than 4.4 times the minimum cross-sectional area of the flash venting.

Description

CARTRIDGE CASE The invention relates to small arms ammunition. More particularly, the invention relates to a cartridge having a case configured for use with a lead-free Boxer-type primer.

The two main forms of small arms ammunition are centerfire and rimfire cartridge-type ammunition. Centerfire ammunition utilizes a metal cup-shaped percussion primer located in the head or base of the cartridge case. Common primers are of the Boxer and Berdan types. The Boxer primer is pre-assembled with an anvil, whereas the Berdan primer is adapted for use with a cartridge case having an anvil formed in the bottom of the primer pocket. Either type includes a primer charge located between the closed end or web of the cup and the anvil. Shotshells typically use a battery cup-type primer. This includes a primer cup containing a charge generally similar to that in a Boxer primer. The primer includes an elongated anvil which extends from a battery cup into which the primer cup is fitted.

Traditionally, primers have featured a lead styphnate-based primer charge. Concerns regarding toxicity of such primers (especially when used in indoor ranges) have led to the development of lead-free primers. A common lead-free primer is based upon diazodinitrophenol (dinol). Exemplary primer compositions are disclosed in U.S. Patent Nos. 5,167,736 and 5,417,160.

A variety of cartridge sizes exist which may be used in pistols, rifles or both. A lesser variety of primer sizes exist. Key primer sizes are commonly known as: "large pistol", "small pistol", "large rifle", and "small rifle" primers. Approximate diameters for such primers are 0.209 (0.531 cm), 0.174 (0.442 cm), 0.210 (0.533 cm), and 0.174 (0.442 cm) inches, respectively. The use of a large vs. small size primer may be influenced or necessitated by the relative size of the propellant charge in the cartridge. As is commonly used in the art, the term "small primer" collectively designates small pistol and small rifle primers while the term "large primer" collectively designates large pistol and large rifle primers. A single size of shotshell primer is presently prevalent and commonly identified as "No. 209" and has a battery cup with a predominate outer diameter in the vicinity of 0.243 inches (0.617 cm).

The inventors have investigated weapon damage which they have associated with the use of certain primer types in certain cartridge sizes. In particular, the inventors have observed that when dinol-based lead-free primer charges are substituted for prior lead styphnate-based primer charges in certain sizes of ammunition, there is damage to the face of the bolt of the weapon firing such ammunition. The inventors believe that the dinol composition generates more gas at a faster rate than does the lead styphnate primer. If there is insufficient venting from the primer into the cartridge, the accumulated pressure from the burning primer is

1 sufficient to drive or recoil the primer cup backward, slightly out of the cartridge, and into the face of the bolt.

The combustion of the propellant in the cartridge, triggered by the combustion of the primer, may then drive the case backward, reinserting the primer within the pocket. The inventors have observed this to be a particularly significant problem in cartridges which utilize "large pistol" lead-free primers, namely .45 Automatic Colt Pistol (ACP) and 10 mm Automatic rounds. The problem is especially significant with certain semi-automatic pistols where the bolt face is not sufficiently hardened. This may not be as severe a problem in cartridges utilizing "small pistol" primers such as most .38 ACP (also designated .380 Auto and 9 mm Kurz), 9 mm Parabellum (also designated 9x19 and 9 mm Luger), and .40 Smith & Wesson (S&W) rounds. With the smaller primer charge in the small pistol primer, existing flash hole dimensions may be sufficient to prevent the primer from recoiling within the pocket. Because the large pistol primer is not substantially longer than the small pistol primer, the increase in size from a small pistol primer to a large pistol primer pocket produces an approximately proportional (linearly) increase in the area over which the primer engages the primer pocket (the primer length multiplied by the primer circumference). With the primer force fit into the pocket, the resistance of the primer to recoil is approximately proportional to this area. However, the recoil force generated by the burning primer acts on the cross-sectional area of the primer which increases as the square of the linear dimension. Thus the increase in recoil force is greater than the increase in the resistive friction force, allowing the recoil force to overcome the resistive friction force.

The pressure peak within the primer is influenced by the amount of venting between the primer pocket and the body of the case. The inventors believe that in many cartridges having cases configured for use with lead-based primers, the venting provided by the existing flash hole may be insufficient to keep pressures below the level which causes recoil of the primer when a lead- free primer is substituted. In such cases where the existing venting is insufficient, the inventors have provided for increased venting such as by increasing the diameter of the flash hole separating the primer charge from the propellant charge.

Additional features and advantages of the invention will be readily apparent from the following description and accompanying drawing.

FIG. 1 is a longitudinal cross-sectional view of cartridge having a case in accordance with the present invention.

FIG. 2 is a chart showing a variety of exemplary cartridge dimensions. FIG. 3 is a longitudinal cross-sectional view of a shotshell having a battery cup primer in accordance with the present invention.

Like reference numbers and designations in the several views indicate like elements.

As shown in FIG. 1, a cartridge 20 includes a case 22, a bullet 24, a propellant charge 26, and a primer 28. In the illustrated embodiment, the case is unitarily formed of brass and is symmetric about a central longitudinal axis 100. The case includes a wall 30 extending from a fore end 32 to an aft end 34. At the aft end of the wall, the case includes a head 36. The head has front and aft surfaces 38 and 40. The front surface 38 and the interior surface 41 of the wall 30, define a cavity configured to receive the propellant charge 26. The head has surfaces 44 and 46 defining an approximately cylindrical primer pocket extending forward from the aft surface 40. The head has a surface 48 defining a flash hole extending from the primer pocket to the cavity. In the illustrated embodiment, the surface 48 and flash hole 49 defined thereby are cylindrical, e.g., of uniform circular cross-section.

The primer 28 includes a metal cup formed as the unitary combination of a sleeve portion 52 and a web portion 54 spanning the sleeve at an aft end of the sleeve.

A dinol-based primer charge 56 is contained within the cup along a forward surface of the web 54. Forward of the primer charge, an anvil 58 is disposed across the cup and has aft and forward surfaces and at least one venting aperture (vent) extending between such surfaces.

In operation, with the cartridge in the chamber of a weapon, a pin 104 carried within a bolt 106 of the weapon is driven forward and strikes the aft surface of the web 54. The impact deforms the web forward and drives the primer charge against the anvil, igniting the primer charge. Hot combustion gases and flames from the burning primer are vented through the vent(s) of the anvil and into the cavity through the flash hole whereupon they ignite the propellant charge. Gas generated by the burning propellant charge drives the bullet out of the case mouth and forward through the barrel 108 of the weapon.

The cartridge may be removed from the chamber via engagement of an extractor (not shown) with an extraction groove 70 formed in the case about the head.

In an exemplary embodiment, the cartridge is a .45 ACP cartridge, with the primer of "large pistol" size. The primer pocket has a diameter Dp of about 0.2093 inches (0.532 cm) and a depth or length Lp of about 0.12 inches (0.305 cm). The primer is countersunk within the pocket (e.g., below flush with the aft end of the head) by a length Lcs of about 0.004 inches (0.010 cm). Even with rounds having the same pocket depth (which rounds may be of the same or different calibers), the countersink depth (or "cap seating") may be varied for purposes including adjusting the sensitivity of the primer. The cup and anvil have respective volumes V_c and V_A of about 0.00135 and 0.000574 cubic inches (0.022 and 0.0094 cm³). Within the cylindrical portion of the pocket a volume is contained within the cup and around the primer. This volume VFP is determined by the volume of the pocket minus the volumes of the cup, the anvil and the countersunk space between the cup and the aft surface of the head. In the exemplary embodiment, V_FP is about 0.002067 cubic inches (0.034 cm³).

The flash hole has a diameter D_H of about 0.15 inches (0.38 cm) and a length L_H of about 0.15 inches (0.38 cm) (the latter being the thickness of a web between the primer pocket and the propellant cavity). This value of D_H results in a cross-sectional area A_H of about 0.0177 square inches (0.114 cm²). An exemplary value for the diameter of the of flash hole of a conventional (designed for lead styphnate primers) .45 ACP cartridge is about 0.08 inches (0.203 cm) which is about 0.00503 square inches (0.032 cm²) in cross-section.

Preferably, the minimum diameter of the flash hole (which is the only diameter if the flash hole is cylindrical) is between about 0.1 inches (0.25 cm) (0.105 inches (0.27 cm) resulting in a 50% increase in cross-sectional area over an 0.08 inch (0.203 cm) hole) and about 0.17 inches (0.43 cm). In one experimental embodiment, a diameter of 0.105 inches (0.27 cm) was just sufficient to avoid damage from primer recoil. In embodiments as 10 mm Automatic cartridges, the same flash hole diameter may be utilized. Other exemplary dimensions as well as those for exemplary conventional cartridges are shown in FIG. 2. The various calculated dimensions shown in spreadsheet format in FIG. 2 may be shown with more digits than are significant. Furthermore, the various values are exemplary and other values may be useful.

FIG. 2 shows exemplary values for seven particular cartridges: .45 ACP, 10 mm, 9 mm, .40 S&W, .38 SPL, .223 Remington (5.56 mm), and .308 Winchester (7.62 mm NATO). The first four are the straight-walled automatic pistol cartridges as previously described. The fifth is a straight- walled rimmed cartridge used primarily in revolvers. The final two are bottlenecked rifle cartridges, utilizing small and large rifle primers, respectively. With the straight cartridges, the maximum internal diameter of the case is approximately the same as the caliber of the bullet. With the bottlenecked cartridges, the maximum internal diameter is greater than the caliber of the bullet, allowing a relatively greater propellant charge to be used to fire a relatively small bullet, thus achieving high bullet velocity.

Thus, in the exemplary .45 ACP embodiment, the maximum internal cross-sectional area of the case is approximately 0.16 square inches (1.03 cm ). Thus, in the exemplary embodiment with a 0.15 inch (0.38 cm) diameter flash hole, the ratio of flash hole cross-sectional area to maximum internal case cross-sectional area is about one to nine. With a flash hole diameter range of about 0.1 to about 0.17 inches (0.25 to about 0.43 cm), the corresponding range of ratios is from about 0.049 to about 0.14. With lower limits on that diameter range of 0.11 inches (0.28 cm) and 0.13 inches (0.33 cm), the associated ranges of area ratio would start at about 0.06 and 0.083, respectively. The degree of flash venting which may be advantageous and/or required is heavily dependent on primer mass and composition. With other factors held constant, primer charges which burn relatively fast and/or emit a relatively large volume of gas will be associated with high degrees of flash venting. For example, a relatively gaseous primer composition is disclosed in U.S. Patent No. 5,466,315, November 14, 1995. That patent identifies an exemplary composition as 45% Dinol, 10% tetracene, 25% Hercules Fines and 20% calcium suicide by weight. With a 0.2 grain (0.013 g) charge of such primer composition in a standard small pistol primer cup, the degree of flash venting provided by the standard 0.080 inch (0.203 cm) flash hole may be insufficient for reliable resistance to primer recoil. By way of further example, such a primer is advantageously associated with a flash hole of at least 0.09 inches (0.229 cm) in diameter. An exemplary 0.098 inch (0.249 cm) hole is believed to provide approximately equivalent resistance to primer recoil as does a hole of 0.14 inches (0.356 cm) in combination with a large pistol primer having a 0.33 grain (0.021 g) charge of priming mix such as disclosed in U.S. Patent No. 5,466,315. An exemplary embodiment of a 9mm cartridge including such a flash hole has a maximum internal cross-sectional area of its case of approximately 0.099 square inches (0.64 cm²). The ratio of the exemplary flash hole cross-sectional area to maximum internal case cross-sectional area is about 0.076 . With a flash hole diameter range of about 0.09 to about 0.14 inches (0.23 to about 0.36 cm), the corresponding range of ratios is from about 0.064 to about 0.16. With lower limits on that diameter range of 0.095 inches (0.24 cm) and 0.10 inches (0.25 cm), the associated ranges of area ratio would start at about 0.071 and 0.079, respectively. Exemplary ranges for flash hole sizes in cartridge cases using small and large rifle primers may be similar to those given hereinabove relative to small and large pistol primers, respectively.

FIG. 3 shows a cartridge in the form of a shotshell 120. Except for flash hole size discussed below, the geometries and dimensions of the shotshell and its primer may be similar to or the same as any of a number of conventional shells (e.g. 20, 12, and 10 gage and the like) and primers (e.g. No. 209 - size primers). The shotshell has a hull including a Reifenhauser tube 122, a basewad 124 and a metallic head 126. In the illustrated embodiment, the tube and basewad are separately formed of plastic although they may be unitarily formed. The basewad is located within the tube, proximate the aft end 128 thereof. An external lateral, primarily cylindrical, surface 130 of the basewad contacts an internal primarily cylindrical surface 132 of the tube. The metallic head has a sleeve portion 134 secured to the tube along aft portion thereof. An internal surface 136 of the sleeve contacts an external surface 138 of the tube. At its aft end, the sleeve flares outward to form a rim of the shotshell which compressively holds the flared aft end 128 of the tube to a beveled shoulder of the basewad. A web 140 spans the sleeve, extending inward from the rim, forming a base of the cartridge. The web 140 has a central aperture 142, adjacent which the web is deformed forwardly. The web contacts a generally annular aft surface 144 of the basewad 124. Contained with the tube and generally forward of the basewad is wadding which, in the exemplary embodiment, is the unitarily formed resilient plastic combination of an aft over-powder cup 146, a compressible mid-section 148 extending forward therefrom, and an over-shot cup 150 extending forward from the mid-section 148 in a forward section of the tube. The over-shot cup 150 contains a load of shot pellets 152, although other projectiles such as a single slug may be utilized. At its fore end 154, the tube is crimped such as via a star crimp 156. The over-powder cup 146 includes an aft- facing concavity which, along with a fore-facing compartment of the basewad, defines a powder chamber 160 containing a propellant charge 162. To ignite the propellant charge, a primer 170 is carried within the basewad. The primer 170 extends through the central aperture 142 of the head and a central aperture 172 of the basewad. The primer includes a forward-facing primer cup having a generally cylindrical sidewall 174 and a web 176 spanning the sidewall and forming an aft end of the primer cup. The primer further includes an aft-facing battery cup having a generally cylindrical sidewall 178 and a web 180 spanning the sidewall at the forward end thereof to define a forward end of the battery cup and primer. The primer cup is press fit within the battery cup adjacent the aft end thereof thus closing the otherwise open aft end. The battery cup is press fit within the basewad extending through the central aperture of the head and into the central aperture 172 of the basewad. Proximate a rim at its aft end, the sidewall 178 is flared outward so that, adjacent the aperture 142, the outer surface of the sidewall matches the local contour of the aft surface of the web 144 of the head adjacent the aperture 142. The primer cup contains a primer charge 182 which may be covered by a foil or other layer and may have a composition similar to those described for the primer charge 56 of FIG.1. An aft-facing anvil 184 has a base held by the battery cup and a tip extending centrally into the primer cup proximate the primer charge. A circular flash hole 186 is located centrally within the web 180 to provide flash venting extending from the interior of the battery cup to the powder chamber 160. When the primer cup is struck via a firing pin as heretofore described, forward deformation of the web 176 causes the primer charge to impact the anvil tip igniting the primer charge. The ignited primer charge is vented through the flash hole 186 to ignite the propellant charge 162. In the exemplary embodiment, the flash hole 186 is a single circular aperture having a diameter in excess of the 0.095 inch (0.24 cm) diameter of a conventional flash hole in a shotshell primer. The flash hole is advantageously about 0.150 inch (0.38 cm) in diameter providing a venting of 0.018 square inch (0.11 square cm). Preferably, the flash venting is in excess of a minimum value of about 0.0079 square inch (0.051 sq. cm). An advantageous range is from about 0.011 sq. inch (0.073 sq. cm) to about 0.027 sq. inch (0.15 sq. cm). In the exemplary embodiment, the base of the anvil has a forward-facing concavity overarching the flash hole. Such a construction is particularly advantageous with the exemplary single circular flash hole. With other anvil constructions, other flash venting arrangements may be advantageous including the presence of multiple flash holes. In the exemplary embodiment, the primer has an overall length of about 0.3 inch (0.76 cm) and the battery cup sidewall outer surface has a diameter about 0.24-0.25 inch (0.612-0.635 cm) and preferably of about 0.241-0.245 inch (0.61-0.622 cm) along a major portion surrounding the primer cup. The flaring of the aft end of the battery cup produces a local diameter of about 0.3-0.32 inches (0.76-0.81 cm). Specifically, a forward portion of the battery cup extending along a length of about 0.15-0.16 inch (0.38-0.41 cm) has an predominate external diameter of about 0.241 inch (0.612 cm). The battery cup, having a uniform wall thickness of about 0.02 inch (0.051 cm) expands slightly behind the forward section to form a pocket for receiving the primer cup. In this area surrounding the primer cup, the battery cup has a predominate external diameter of about 0.245 inch (0.622 cm) until flaring outward at the aft end.

Although the enlarged flash hole provided by the present invention is especially advantageous in cartridge sizes primarily used in large caliber automatic (technically semi-automatic) pistols, it may be applied to other cartridge sizes. Although applied to a brass case, round nose bullet, pistol cartridge, the principles of the invention may be applied to cartridges of other materials, such as those having cases made of other metals including aluminum and steel. Furthermore, although a number of particular embodiments have been described, the claimed invention may be employed other than as specifically described. For example, the flash hole may be other than a cylindrical hole, for example, a square cross-section hole. Furthermore, the principles of the invention may be applied to cartridges and primers yet unknown.

7 While the invention has been described above with reference to specific embodiments thereof, it is apparent that many changes, modifications, and variations can be made without departing from the inventive concept disclosed herein. Accordingly, it is intended to embrace all such changes, modifications, and variations that fall within the spirit and broad scope of the appended claims.

What is claimed is:

Claims

1. A centerfire cartridge case (22), having a central longitudinal axis (100) and comprising the unitarily formed combination of: a wall (30) extending from a fore end (32) to an aft end (34), a mouth defined at the fore end and configured to receive a bullet (24); and a head (36) at the aft end of the wall having a front surface (38) and an aft surface (40), the front surface and wall defining a cavity configured to receive propellant (26), the head having surfaces (44, 46) defining a primer pocket extending forward from the aft surface and having at least one surface (48) defining a flash venting (49) extending from the primer pocket to the cavity, the primer pocket configured to receive a primer (28), characterized in that the flash venting has a minimum cross-sectional area and the primer pocket has a generally cylindrical surface portion configured for engaging the primer, which cylindrical surface portion has a first cross-sectional area, no greater than 4.4 times said minimum cross-sectional area.

2. The case of claim 1 characterized in that said first cross-sectional area is no greater than about 3 times said minimum cross-sectional area.

3. The case of claim 1 characterized in that said first cross-sectional area is about 1.6 to about 2.4 times said minimum cross-sectional area.

4. The case of claim 1 characterized in that said cylindrical portion has a diameter of about .209 inches (5.31-5.32 mm).

5. The case of claim 1 characterized in that said case is a non-bottlenecked case and is dimensioned to receive a bullet of a particular caliber between about 10 mm and 11.5 mm.

6. The case of claim 1 characterized in that the case is a size of one of a group of cartridge case sizes consisting of .45 ACP and 10 mm Automatic.

7. The case of claim 1 characterized in that the case is formed of brass and configured to receive a Boxer-type primer.

8. The case of claim 1 characterized in that the flash venting consists of a single flash hole.

9. A centerfire cartridge case (22), generally symmetric about a longitudinal axis, and comprising the unitarily formed combination of: a wall (30) extending from a fore end (32) to an aft end (34), and having an interior surface (41) and an exterior surface, the interior surface having a maximum diameter greater than 0.38 inches (0.97 cm) and defining a mouth at the fore end configured to receive a bullet (24); and a head (36) at the aft end of the wall having a front surface (38) and an aft surface (40), the front surface and the interior surface of the wall defining a cavity configured to receive propellant (26), the head having surfaces (44, 46, 48) defining a primer pocket extending forward from the aft surface and a flash hole (49) extending from the primer pocket to the cavity, the primer pocket configured to receive a Boxer- type primer (28), characterized in that the flash hole has a minimum cross-sectional area no less than 0.049 times said maximum cross-sectional area.

10. The case of claim 9 characterized in that said minimum cross-sectional area is no less than 0.06 times said maximum cross-sectional area.

11. The case of claim 9 characterized in that said minimum cross-sectional area is no less than 0.083 times said maximum cross-sectional area.

12. The case of claim 9 characterized in that said minimum cross-sectional area is about one ninth said maximum cross-sectional area.

13. A centerfire small arms cartridge (20) comprising: a Boxer-type primer (28) having: a cup having: a sleeve portion (52) having a front end and an aft end; and a web portion (54) at the aft end of the sleeve portion; an interior surface; and an exterior surface an anvil (58) disposed across the cup and having an aft surface and a forward surface; and a primer charge (56) contained within the cup between the web and the anvil; a bullet (24);

10 a case (22) comprising the unitarily formed combination of: a wall (30) extending from a fore end (32) to an aft end (34), a mouth defined at the fore end receiving the bullet; and a head (36) at the aft end of the wall having a front surface (38) and an aft surface (40), the front surface and wall defining a cavity configured to receive propellant (26), the head having surfaces (44, 46, 48) defining a primer pocket extending forward from the aft surface and a flash hole (49) extending from the primer pocket to the cavity, the primer pocket receiving the primer; and a propellant charge 26 contained in the case between the bullet and the head characterized in that the flash hole (49) has a minimum cross-sectional area and the primer pocket has a generally cylindrical surface portion (44) engaging the primer, which cylindrical portion has a first cross-sectional area within which a first volume is contained within the cup and around the primer, a ratio of such minimum cross-sectional area to such first volume being greater than about 4.4/inch (1.7/cm).

14. The cartridge of claim 13 characterized in that the ratio of such minimum cross- sectional area to such first volume being between about 5.5/inch (2.2/cm) and about 11.0/inch (4.3/cm).

15. The cartridge of claim 13 characterized in that the ratio of such minimum cross- sectional area to such first volume being about 8/inch (3.1/cm) to about 9/inch (3.5/cm).

16. The cartridge of claim 13 characterized in that the primer charge is dinol-based and substantially lead-free.

17. The cartridge of claim 13 characterized in that said case is non-bottlenecked and the bullet is of a caliber between about 10 mm and about 11.5 mm.

18. The cartridge of claim 13 characterized in that the flash hole is primarily defined by a cylindrical surface of a cross-sectional area equal to said minimum cross-sectional area.

19. An ammunition cartridge, comprising: a hull including:

11 a tube (122), extending from an aft end to a fore end and having an exterior surface; a metallic head (126) having: a sleeve portion (134) secured to the tube along an aft section of the tube; and a centrally apertured web portion (140) spanning the sleeve portion and forming a base of the cartridge; and a basewad (124) within the tube, the basewad located proximate the aft end of the tube and having: an aft surface (144) contacting the metallic head; and a fore surface, extending from a an inner portion s rounding a central aperture to an outer portion proximate the tube; at least one projectile (152) carried within the tube; a propellant charge (162) in a powder chamber (160) bounded in part by the basewad; and a primer (170) carried within the basewad and having: an aft-facing battery cup having a sidewall (178) and a web (180); a forward- facing primer cup having a sidewall (174) and a web (176), the web forming an aft end of the primer cup and the primer cup sidewall having an outer surface bearing against an inner surface of the battery cup sidewall (178); a primer charge (182) contained within the primer cup; and an anvil (184) within an interior of the battery cup; characterized in that the battery cup has at least one surface defining a flash venting (186) extending from the interior of the battery cup to the powder chamber, the flash venting having a total cross-sectional area in excess of 0.051 sq. cm (0.0079 sq. in.).

20. The cartridge of claim 19 characterized in that : the tube is separately formed from the basewad; and the flash venting has a total cross-sectional area in excess of 0.073 sq. cm (0.011 sq. in.) and less than 0.15 sq. cm (0.027 sq. in.).

21. A shotshell primer (170) having : a battery cup having a sidewall (178) and a web (180); a primer cup having a sidewall (174) and a web (176), the web (176) forming an at end of the primer cup and the primer cup sidewall (174) having an outer surface bearing against an inner surface of the battery cup sidewall (178); a primer charge (182) contained within the primer cup; and

12 an anvil (184) within an interior of the battery cup; characterized in that the battery cup has at least one surface defining a flash venting (186) extending from the interior of the battery cup to an exterior of the battery cup, the flash venting having a total cross-sectional area in excess of 0.051 sq. cm (0.0079 sq. in.).

22. The shotshell primer of claim 21 characterized in that the flash venting consists essentially of a single central flash hole (186) in the web (180) of the battery cup.

23. The shotshell primer of claim 21 characterized in that the battery cup sidewall (178) has an outer surface which, along a major portion surrounding the primer cup, has a diameter of about 0.612cm (0.24 in.) to about 0.635cm (0.25 in.).

24. A centerfire small arms cartridge (20) characterized by: a Boxer-type primer (28) selected from the group of sizes consisting of small pistol, large pistol, small rifle, and large rifle; a bullet (24); a case (22) comprising: a wall (30) extending from a fore end (32) to an aft end (34), a mouth defined at the fore end receiving the bullet; and a head (36) at the aft end of the wall having a front surface (38) and an aft surface, the front surface and wall defining a cavity configured to receive propellant (26), the head having surfaces (44, 46, 48) defining a primer pocket extending forward from the aft surface and a flash hole (49) extending from the primer pocket to the cavity, the flash hole having a minimum cross-sectional area of at least 0.041 sq. cm (0.00636sq. in.) and the primer pocket containing the primer; and a propellant charge (26) contained in the case between the bullet and the head.

25. The cartridge of claim 24 characterized in that the primer is a small primer and the minimum cross-sectional area is between 0.046 sq. cm (0.0071 sq. in.) and 0.1 sq. cm (0.015 sq. in.).

26. The cartridge of claim 24 characterized in that the primer is a large primer and the minimum cross-sectional area is between 0.086 sq. cm (0.013 sq. in.) and 0.15 sq. cm (0.023 sq. in.).

13