It uses a P90 gearbox. A 1500mah nicad is in the reciever tube behind the gearbox. An mp5 hop up is attached to the gearbox via a brass bracket. The hop up is adjusted by the philips screw you can see in the 4th pic. The only real M3 parts are the flash hider and magazine (with a thompson hi cap installed) pistol grip is easily removed by unscrewing what would be the oiler on the real gun. Inside the grip is the trigger mechanism, fuse and charging jack. The trigger hits a micro switch which activates a relay (blue box in photos) that powers the motor. I don't think the switch alone would handle the current for very long.
The tappet plate in the gearbox is modified to lower the nozzle and allow the gearbox to be raised higher in the reciever. The tappet plate is shortened at the front and reinforced with metal pins.
