Airsoft supply store
Electrically powered airsoft guns use a spring-loaded piston pump just like spring guns, but instead of manual operation they typically use portable rechargeable battery packs to power an internal electric motor, which transmit through a gearbox to compress the pump spring and propel/load the pellets in a cyclic fashion. Selective fire options among automatic, 3-round burst and semi-automatic operations are all possible, which gives these guns the popular name "automatic electric guns", or AEGs.[3] These guns often attain muzzle velocities from 150 to 650 ft/s (46 to 198 m/s) and rates of fire (RoF) between 100 and 1500 rounds per minute. They are the most commonly used and widely available type of airsoft gun.
The AEGs were developed in Japan and the Japanese company Tokyo Marui is credited with creating the original gearbox system. In a Tokyo Marui AEG, the motor drives a train of three gears mounted inside a gearbox, which then loads a pump piston against a spring. Once the spring is released, it pushes the piston plunger forward through the pump cylinder to propel a pellet resting within the chamber forward through the barrel and out of the muzzle. Many manufacturers have now more or less replicated this basic model, adding reinforced parts or minor improvements.