Abstract: For firing bullets or cartridges of different lengths but the same caliber, there is provided a barrel which is threaded at both ends and reversible, with different-length bores in each end. There is desirably also a protective cap for the threads at the distal end of the firearm, and also, at each end of the barrel, a lug or projection with opening therein to aid in securing the reversible barrel onto the part of the firearm proximal to the user.

Abstract: A firearm capable of firing different-sized cartridges by the use of a detachable chamber having a plurality of bores extending therethrough. Each bore is adapted to receive a different-sized cartridge. The chamber is carried on a firearm receiver and can be positioned such that any one of the aforesaid bores in the chamber is aligned with the axis of the receiver.