Problem with my M4

Well, I think the gearbox might be locked. When I try to shoot it, I can feel the motor try to turn but nothing happens. I know the battery isnt dead because I used a battery that was working in another gun.

Any advice?

Burn it.....lol

No take of the upper receiver and then gently push the piston back with a small thin stick until it lets go.(you must pull the trigger as you push back. Make sure it only lets go of the piston NOT REENGAGE TILL AFTER YOU TAKE THE STICK OUT.) But you must fallow throw or you make things even worse.

Thats just a fast way to do it.

Good Luck