Abstract: A firearm can have a bolt having a plurality of locking lugs that are configured to have a shear area that is at least approximately 1.3 times that of a standard M16/M4. A piston can be formed on the bolt and can have a plurality of rings that are configured to cooperate with the piston to mitigate gas leakage past the piston. Each of the rings can have a key formed thereon and a gap formed therein such that the gap of one ring is configured to receive at least a portion of the key of another ring. The bolt carrier can have a double cut cam.

Abstract: A drum magazine for a gun has a circularly cross-sectioned housing (40) with a feed throat (415) extending from the housing for releasing cartridges and concentric sprockets (42, 43, 44) having serrations nesting cartridges. A torsion spring (46) is arranged to rotatingly drive the sprockets and feed ramps (434, 441, 455, 455', 471, 471') are provided for assisting the cartridges to traverse from the sprockets to the feed throat (415).The feed throat has two lips and one of the lips (417) is pivotally biassed to act as a one way valve such that in one position cartridges are prevented from being ejected in a direction perpendicular to the housing axis and yet cartridges may be inserted into the housing in a direction perpendicular to the housing axis.

Abstract: A drum magazine for a gun has a housing with a feed throat extending from the housing and within the housing are mounted concentric sprockets. The sprockets have serrations for nesting cartridges and each sprocket is independently rotatable with stops for limiting the rotation of the outer sprocket and stops limiting rotation of the intermediate sprocket. A latch is arranged to prevent rotation of the outer sprocket in a counter direction to the direction of feeding cartridges out of the magazine until the intermediate sprocket is rotated in the counter direction a predetermined amount. A connector is connected to the outer sprocket and passes through the outer sprocket to engage with the cartridges nested in the intermediate sprocket so that by virtue of the connector, the sprockets rotate together. A similar connector is provided between the intermediate sprocket and the inner sprocket. A U-shaped pusher is provided to push the last few remaining cartridges in the magazine out of the feed throat.