Gas blowback pistols

Gas blowback pistols are designed to use HFC134A refrigerant to fire BBs and also to blow back the slide, mimicking the recoil of automatic hand guns. Refrigerant is sold in canisters similar to small propane canisters used in portable gas range. Propane based "Green" gas can be used, but could damage the replica due to higher pressure it exerts to mostly plastic parts used in gas blowback replicas.