A portable electric motor driven air gun powered by a power source. The motor is coupled to a lead screw, which drives a piston. The piston compresses air in a chamber producing high-pressure air. When sufficient energy is stored within the air stream by the piston a valve opens which releases the air to act on the projectile. The compressed air is used to push a projectile such as a paintball, an airsoft ball, a “bb”, or a pellet through a barrel. The lead screw is then reversed and the piston is reset for the next shot. The piston is preferably coupled to a feeding mechanism to facilitate positioning of the projectile for firing. The direction speed and operative modes of the gun are preferably controlled with an electric circuit. The power source is preferably rechargeable and allows the air gun to be operated completely independent from either a wall outlet or a compressed air supply.