Gas Blowback Rifle(GBBr)-Gas-powered airsoft guns use the pneumatic potential energy stored within compressed gas to drive the shooting mechanism, and thus operate according to an entirely different design principle to spring- or electrically powered airsoft guns. The most common type seen is the gas blowback (GBB) guns. These gas guns use an internal canister (usually within the magazine) that upon trigger-pull releases the prefilled bottled gas via a series of valves to propel the pellet and generate a blowback, which simulates recoil and cyclically loads the next shot. They are capable of both automatic and semi-automatic operation.