Electric Air Gun
An airsoft gun that uses a spring-powered piston to compress air in order to propel the BBs. A battery-driven electric motor cocks the spring after each shot and it can do this very fast to achieve realistic rates of full-automatic fire. The mechanism is very reliable, even in a bit colder weather and easy to maintain. On the other hand, it is not as realistic as a gas-blowback action and cannot be built inside anything smaller than a medium-sized submachine gun. Still, electric guns are nowadays the industry standard.