FIELD OF INVENTION

This invention relates to cartridge ammunition, in particular, subsonic cartridge ammunition such as small to medium calibre ammunition.

BACKGROUND TO INVENTION

Generally accepted design criteria used in the design of small to medium calibre subsonic ammunition, include the design of the projectile such that a portion of the projectile which is located within the cartridge case of the ammunition, occupies a minimal volume within the cartridge case so as to provide for maximum internal free volume for expanding propeliant gases. It will be appreciated that a reduction in the internal free volume within the cartridge case will result in an increase in gas pressure within the free volume. A relatively large free volume within the cartridge thus acts as a pressure attenuator for propeliant gas pressure peaks within the cartridge case. Exposure of weapon chambers to high pressure peaks is clearly unsatisfactory as such exposure may cause damage to the firing weapon and also result in possible injury or death to operators of a firing weapon. As evidence of the abovementioned design criteria, weapon manufacturers are generally unwilling to endorse the use of enhanced ammunition configurations on their weapons where such enhancements may include, for example, heavier projectiles or extended firing ranges, as the potential for failure is too high due to resultant peak weapon chamber pressures in excess of standard pressures which the weapons were designed to endure in the field.

It is an object of the present invention to provide cartridge ammunition which meets the abovementioned design criteria and more specifically, which provides for attenuation of high pressure peaks in the weapon chambers of firing weapons.

SUMMARY OF INVENTION

According to the invention there is provided cartridge ammunition including: a cartridge including: a) a cartridge case having a cylindrical sidewall having an open front end and a base wall extending across the sidewall at a rear end of the cartridge case; b) a primer chamber adjacent the base wall in which an initiating primer is held; and c) high and low pressure chambers delimited by walls within the cartridge case for expanding propellant gases; and a projectile including a projectile body having a front end and a rear end which is sealingly located within the front end of the cartridge case, the cartridge ammunition being characterized in that the projectile defines a circumferential skirt formation at the rear end of the projectile body which projects rearwardly from the projectile body and which includes sealing means for forming a gas- tight seal with the sidewall of the cartridge case.

The projectile may include an annular seal which extends circumferentially around the projectile for forming a gas-tight seal with the sidewall of the cartridge case.

The annular seal may be located along an external side of the skirt formation of the projectile. The external side of the skirt formation may define an annular groove providing a seat within which the annular seal is located.

The projectile may include an additional annular seal which extends circumferentially around the projectile for forming an additional gas-tight seal with the sidewall of the cartridge case.

The additional annular seal may be located along an external side of the projectile body at a location longitudinally spaced from the annular seal and parallel thereto. The external side of the projectile body may define an annular groove defining a seat within which the additional annular seal is located.

The projectile body may define an annular recess into which a front end region of the cartridge case is crimped inwardly so as to engage the projectile body within the annular recess.

The annular groove for the additional annular seal may be defined within the annular recess. BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention are described hereinafter by way of a non-limiting example of the invention, with reference to and as illustrated in the accompanying diagrammatic drawings. In the drawings:

Figure 1 shows a sectional side view of cartridge ammunition in accordance with the invention;

Figure 1a shows enlarged detail view I of the cartridge ammunition of Figure 1 ;

Figure 2 shows a sectional end view of the cartridge ammunition of Figure 1 as sectioned along section line ll-ll;

Figures 3 to 6 show, in sequence, the manner in which a projectile of the cartridge ammunition separates from the cartridge case thereof when the cartridge ammunition is fired in the barrel of a firing weapon, Figures 3a-6a showing enlarged detail views A-D of Figures 3-6, respectively.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to the drawings, cartridge ammunition in accordance with the invention, is designated generally by the reference numeral 10. The cartridge ammunition is in the form of subsonic small to medium calibre ammunition having a high-pressure, low- pressure propulsion system for expelling the projectile from the cartridge. The cartridge ammunition 10 includes, broadly, a projectile 12 and a cartridge 14. The cartridge 14 includes a cartridge case 16 having a cylindrical sidewall 18 having a front end 20 and a rear end 22, with the front end 20 being open so as to receive the projectile 12 therein. The cartridge case has a base wall 24 which extends across the sidewall at its rear end.

A primer chamber 26 is located within the base wall 24, in which an initiating primer is held. The primer chamber is centrally located within the base wall of the cartridge case and is configured to receive a firing pin of a firing weapon, which extends into the primer chamber for initiating the primer.

The cartridge includes a high pressure chamber 28 which houses the propellant charge and a low pressure chamber 30 surrounding the high pressure chamber. More specifically, the cartridge includes a body insert 32 which defines a boundary between the high pressure chamber and the low pressure chamber. The body insert 32 has a hollow cylindrical configuration with a domed distal end defining a number of venting holes 34 therein allowing for venting of propellant gases from the high pressure chamber to the low pressure chamber. The high pressure chamber body insert is centrally located within the cartridge case and has an externally screw-threaded proximal end which is screwed into a complementary internally screw-threaded socket 35 defined in a boss 37 projecting from the base wall of the cartridge case. The projectile 12 includes a projectile body 36 having a front end 38 and a rear end 40 which is sealingly located within the front end of the cartridge case. The projectile body includes an O-ring seal 44 near the rear end thereof which extends circumferentially around the projectile body for forming a gas-tight seal with the sidewall of the cartridge case. The projectile body defines an annular recess 45 in which an annular groove 47 is defined which provides a seat for the O-ring seal 44. A front end region 47 of the cartridge case is crimped inwardly so as to engage the projectile body within the recess 45 thereby releasably locating the projectile with respect to the cartridge case.

The projectile defines a circumferential skirt formation 48 at the rear end of the projectile body which projects rearwardly from the projectile body and which includes an O-ring seal 46 which extends circumferentially around the skirt for forming a gas-tight seal with a sidewall of the cartridge case. An annular groove 50 is defined in an external side of the skirt formation 48 providing a seat for the O-ring seal 46.

The projectile 12 defines a longitudinal axis A which extends along a centre line of the projectile between its front and rear ends. The O-ring seals 44 and 46 are disposed parallel and longitudinally-spaced relative to one another.

With reference to Figures 3 to 6 of the drawings, the cartridge ammunition is shown located within a barrel 52 of a firing weapon. Figures 3 to 6 show, in sequence, the manner in which expanding propellant gases within the cartridge case of the cartridge ammunition exert pressure on the projectile causing it to be expelled from the cartridge case.

In field trials conducted with the cartridge ammunition in accordance with the invention, the Applicant has noted that peak gas pressures are generated when the ammunition is fired within 50 to 70 microseconds after firing and thereafter begin to dissipate within 10 to 15 microseconds. The extended rear skirt formation of the projectile ensures that the sealing points provided by the O-ring seals 44 and 46 of the projectile clear the cartridge case only after the peak pressure has begun to dissipate. In addition, the free volume defined within the low pressure chamber adjacent a rear end of the projectile increases in volume as the projectile moves out of the cartridge thereby resulting in attenuation of peak gas pressures within the cartridge. As a result, the weapon chamber of the firing weapon is not exposed directly to the high pressure peaks that are evident when firing conventional subsonic ammunition.

In order to achieve the pressure attenuation advantages of the cartridge ammunition, the cartridge case has a structural rigidity and strength such that it will be able to withstand the internal peak pressures within the cartridge without failure or expanding to a full contact condition with the walls of the weapon chamber which would result in the same peak forces being transferred to the weapon chamber and barrel assembly. The cartridge case thus acts in a manner wherein it becomes a substitute for the barrel during the first phase of movement of the projectile relative to the cartridge case wherein the projectile remains within sealing engagement with the cartridge case and there is a closed retention of pressure within the cartridge case.