Firing problem

[Ande]

Me and my son were out back yesterday target shooting with our M4A1, when it just stopped firing and started this screeching noise, i looked on youtube for some advice and saw somehwere to adjust the allen screw in the bottom of the grip, that just lessened the screeching one way or stopped the gun altogether the other way, so i stripped the gearbox to see if i could find any damage, everything looks fine apart from some wear on the last 2-3 maybe 4 teeth, i have stripped it down and put it back together twice just to double check i had assembled it right, still does it, motor got very hot so i disconnected the battery and put it all back together, any ideas what it could be? it all looks fairly simple inside so i can't see what has happened.

[Lambster]

Maybe the motor seized?

Try taking connecting the motor but not put it in the pistol grip and see if it spins on.

Also, go in the gearbox, remove the piston and check your gears spin freely with little resistance. If there's resistance then check for damage, you might need new gears. Shim and regrease while you're in it too.