A portable motor driven air gun powered by a power source includes a motor that is coupled to a linear motion converter which drives a piston. The piston compresses air in a chamber against a forward air compression valve producing high-pressure air. When sufficient energy is stored within the air stream by the piston, the compression valve opens which releases the compressed air to push a projectile through a barrel. The engagement and disengagement of the linear motion converter and the connected piston to the motor can be controlled using sensors. The linear motion converter further is coupled to a bolt thru a lost motion device to facilitate positioning of the projectile for firing. The direction speed and operative modes of the gun may be controlled with an electric circuit. The power source is preferably rechargeable, allowing the air gun to be operated independent from either a wall outlet or a compressed air supply.