Abstract: An automatic pistol is constructed with a more or less conventional frame and more or less conventional barrel detachably mounted to the frame. The frame and barrel have interfitting portions in cooperative engagement to support the barrel in longitudinal alignment on the frame. The frame is provided with a seating surface for the bottom of the barrel, an abutment surface against which the breech end of the barrel abuts, and a well, forward of the abutment surface, into which a barrel block loosely fits. The barrel block is attached to depend from the barrel. A longitudinal bore through the barrel block partially registers with a corresponding threaded bore through the frame forward of the barrel block. The forward opening of the bore in the barrel block is countersunk, and the axis of this bore is slightly above the axis of the threaded bore with respect to the axis of the barrel.

Abstract: In an autoloading firearm, reloading is actuated by firing gases which are tapped from near the muzzle end of the barrel into a tubular magazine secured below the barrel. A reciprocating piston located inside the magazine is connected to a reloading mechanism and is driven to actuate the mechanism by the tapped gases. A cylindrical obturator is oppositely driven by the gases to scrape the interior of the magazine and serves as a valve to vent the gases.

Abstract: A coupling, normally of tubular construction, is adapted at one end for connection to the lower end of the side supports of a pack frame. The other, or second, end of the coupling is adapted for connection to hip-belt attachment means. The shoulder-to-hip length of the pack frame may be adjusted by selectively varying the distance between the second end and the point of connection of the coupling to the side support members of the frame.