Problem gun.... Just bought a second hand electric TM m733..Worked fine for a couple of hundred shots and now it will only fire if I wind the mag as I am firing.Tried the other two mags that came with it that dont have winders and it wont fire them at all...Stripped the gun down, no obstructions and the piston is working fine, only thing I have changed is the battery which is a 8.5V same as the gun came with, Has anybody got any ideas???....Thanks