Patent ID: 8443730

Claim:
A high strength polymer-based cartridge casing enclosing a volume, comprising: a first end having a mouth; a neck extending away from the mouth; a shoulder extending below the neck and away from the first end; a propellant chamber extending below the shoulder, opposite the neck; and a back end extending below the propellant chamber, comprising: an extraction groove and a rim on an end of the cartridge casing opposite the mouth; wherein the shoulder comprises: an outside shoulder sloped at an acute outside shoulder angle in relation to a center axis extending longitudinally along the cartridge and passing through a center of the mouth, and an inside shoulder sloped at an acute inside shoulder angle in relation to the center axis, and separated from the outside shoulder by a shoulder thickness, wherein the outside shoulder angle and the inside shoulder angle are not equal, and wherein the inside shoulder does not contact a base of a projectile disposed within the neck of the cartridge casing; wherein the neck permits the base of the projectile to extend into the propellant chamber past at least a portion of the inside shoulder, and wherein the inside shoulder angle is greater than the outside shoulder angle.