A firearm includes a receiver with a socket defined by a forwardly extending circumferential rim having an inner surface, a barrel extending from the socket of the receiver and terminating in a muzzle, and a cocking lever housing carried above the barrel. A partial tubular body is received over the barrel with a rearward end abutting the receiver at the forwardly extending circumferential rim. A clamp element is carried by the partial tubular body and is movable between a release position and an engaged position in which a clamp end of the clamp element frictionally engages the inner surface of the circumferential rim.