Abstract: A gun comprising a frame, a barrel, and a slide. The barrel and the slide being slidably mounted to one another and to the frame for movement between a retracted position and an extended position; the barrel having a bore and having a gas port communicating with the bore for allowing gas to pass from the bore when the gun is fired; the gun having a chamber communicating with the gas port when the barrel and slide are in the retracted position and for receiving gas from the gas port when the gun is fired to cause the barrel and the slide to move from the retracted position to the extended position in a direction opposite the recoil of the gun when the gun is fired.