Spring-powered airsoft guns (or "air-cocking guns" as called by Tokyo Marui) are single-shot devices that use the elastic potential energy stored within a compressed coil spring to drive a piston air pump, which is released upon trigger-pull and rapidly pressurizes the air within the pump cylinder to in turn "blow" pellets down the gun barrel.
These guns are almost identical (though simplified and underpowered) in design to spring-piston air guns and have the same operation principles. The user must manually recompress the spring under stress prior to each shot, typically by pulling back the slide (pistols), bolt handle (rifles) or forend pump (shotguns) on the weapon, which cocks and readies the gun. Because of this, spring guns are incapable of automatic or semi-automatic firing by design.
Spring-powered airsoft guns are generally not as powerful as gas-powered ones, but are more powerful than electric airsoft guns because stiffer springs can often be used without the worry of overloading any motor-gearbox, although some spring shotguns and bolt-action rifles can be very powerful with muzzle velocities up to 400–700 ft/s (120–210 m/s). Spring guns are generally inexpensive (except the high-power sniper rifles and shotguns), and may not last long (depending on the build quality) due to the tension exerted on the gun parts by the recoiling of a powerful spring. However, many spring guns can be modified and upgraded to last longer and shoot more powerfully.