A semiautomatic pneumatic gun is provided incorporating a reciprocatable striker-barrel which performs the normal functions of a barrel and a striker, sliding during firing from a cocked position in response to the urging of a striker power spring to impact upon a normally closed valve, which impact releases compressed gas for propelling a projectile from the gun and for recocking the gun. A slidable bolt serves to transfer the impact of the striker-barrel to the valve, and functions as a piston moving in a cylindrical recocking chamber in response to the urging of gas released by the valve to move the striker-barrel back to the cocked position.