Thin walled, two component cartridge casing

Abstract

A cartridge or ammunition casing is made of two components, one forming the outer casing sleeve and head end and the other comprising a plug seated within the head end to protect the outer casing material from propellant gases. The outer cylindrical sidewall and end panel of the casing may be made of a material selected from the group consisting of stainless steel, steel, pre-coated carbon steel, brass or brass-type alloys, aluminum, hardened aluminum alloys, and suitable polymeric plastic material such as nylon derivatives and VECTRA™. The inner plug may be made of a material selected from the group consisting of aluminum, brass, steel, stainless steel, and suitable polymeric materials.

Description

[0001]This invention pertains to the field of ordnance. More particularly, it describes a cartridge casing and process for manufacturing the same which is directed towards cartridge casings typically used in small and artillery caliber ammunition.BACKGROUND OF THE INVENTION[0002]Cartridge casings used in small caliber to artillery caliber weapons provide the function of containing the other major components of the cartridge, including propellant, projectile or bullet and primer. In addition to being a container, the casing must expand slightly and act as a seal to prevent gases, generated by the propellant, from leaking from the forward or mouth end of the casing, along the sidewall of the casing, and through the breach or bolt face at the rear of the casing. The head end of the casing must also absorb the striking force of the firing pin without deforming excessively.[0003]In the case of rimless cartridges, a portion of the head end typically will extend beyond the support of the c...

AI Technical Summary

Benefits of technology

[0021]According to another preferred variant, the inner plug engages with the inner surface of the casing sidewall through an interference fit. One advantage of the interference fit, e.g. having a sealing, preferably voidless, contact between the inside surface of the outer casing sidewall and the outside surface of the plug, is to prevent propellant gas on firing from having access to the head end. Another advantage of providing such a coupling between the plug and casing sidewall is that it will help ensure that both parts are extracted as a unit from the chamber after firing. Alternately, to keep the plug in place within the casing, the casing sidewall may be given a slight inward taper towards its forward end, forward of the plug, after the plug is fitted in place. Further or alternately, an inwardly protruding ring may be formed into the casing sidewall above the upper boundary of the plug to prevent shifting of the plug.

[0039]The current invention also permits the use of relatively thin stainless steel or pre-coated carbon steel as an outer material, providing the strength and even the appearance of brass with the proper coatings. By using a somewhat more expensive per pound, but lighter, aluminum inner plug to provide the reinforcement normally provided by a heavier-based brass or steel conventional casing head end, the current invention can provide savings in overall weight.

Problems solved by technology

As observed in U.S. Pat. No. 2,774,283 by Harvey, the bolt face of such a typical weapon supports and rests against the base or head of the cartridge but does not completely provide support for sealing-in the gases.

The large number of steps in the process and the scrap produced, e.g. during machining the extractor groove, substantially add to the end item cost.

However, in the smaller sizes used in rifles, machine guns and other man-portable high velocity systems, aluminum has not been shown practical.

Under the high pressures and physical stresses encountered in such systems, aluminum has been shown to catastrophically fail in the event of even minor material defects.

The failure mode often results in ignition of the aluminum, causing a “burn through” that can be hazardous to the user.

Numerous attempts have been made to mitigate this behavior through the use of coatings and ablative materials (e.g. U.S. Pat. No. 3,765,297 by Skochko et al), but those methods have not been shown to be fully reliable.

Similar configurations have been tried for high-pressure casings, but they have required heavier base cups to retain the high pressures and attachment to the plastic sidewall to the metallic base cup is a problem.

Under the greater temperatures and more severe physical environments experienced in military weapons these designs have shown a propensity to fail at the joint of the plastic-to-metal base, causing jammed or damaged weapons.

All-plastic cases have also not been shown to be as capable of sustaining the high pressures experienced in small caliber cartridges.

Some applications have been successful, e.g. low pressure blank / training ammunition, but in general, success has not been achieved with higher pressure, conventional, ball / tracer ammunition.

However, the process used to manufacture a steel casing requires even more operations than that used for brass.

However, this still requires performing all the major operations, including applying the lubrication coatings needed for forming steel casings from thicker initial billets.

However, the base cup is not of a design to assist the outer shell in resisting gas pressures in the vicinity of the head end particularly when exposed to the high pressures associated with modern propellants.

The '030 patent ostensibly provides a cartridge that is not substantially reinforced or protected from propellant gas pressure at its base end because of the low structural strength of the paper filler.

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