Abstract: A rapid-fire B.B. pellet-type machine gun operated from a source of gas propellant preferably a canister of liquefield gas, has a trigger-operated valve releasing propellant gas from the source to a pellet containing magazine for projecting the pellets in rapid succession through a barrel passageway to be ejected from the gun at high speed at a target to which the gun is pointed. The pellets underlie and surround a sleeve in the magazine acting as a cofferdam to maintain a local level of the pellets below the gas inlet and the gas outlet so that the gas will impinge against and actuate the pellets causing them to be successively swept into the gas outlet for discharge through the barrel.