Abstract: A gas-powered pistol has a frame with a forwardly opening barrel passage that extends through much of the length of a barrel portion of the frame wherein a reciprocally movable barrel is housed. Side-by-side magazine and gas supply passages extend from the barrel passage through a grip portion of the frame for receiving therein a reloadable magazine and a replaceable pressurized gas cylinder. The frame is formed from metal that is die-cast about a pre-machined metal insert located at the juncture of the barrel and gas supply passages. The insert provides an inlet into which a seal piercing assembly is threaded for receiving pressurized gas from the gas cylinder, and an outlet into which a valve assembly is threaded that slidably supports the breech end of the barrel. The barrel carries a hammer mass that is engaged by a trigger-mounted sear for moving the barrel forwardly in opposition to the action of a firing spring when the trigger is pulled.