Patent ID: 8381655

Claim:
A method for forming a rifle cartridge casing comprising the steps of: (a) forming a cylindrical blank from an aluminum alloy having a tensile strength greater than 80,000 psi, the blank having a proximal end, an open distal end, a circular cross-section, an external diameter and a longitudinal axis; and (b) rotating the blank about its longitudinal axis at a rate greater than 500 rpm and forcing the distal end of the blank into at least one die, the die having a bore with an opening diameter capable of accepting the distal end of the blank, the bore further having progressively reduced interior diameters which are less than the external diameter of the distal end of the blank; wherein the forcing of the distal end of the blank into the at least one die in step (b) results in the finished cartridge casing having a distal end with an external diameter which is less than the external diameter of its proximal end.