[screwdriver]

firstly try another battery, i found the same problems when i switched to using nimh from nicad.
the batteries gave no warning of going flat and i was convinced the gun was jamming.
i also have the tm m4a1 and occasionally it jams on semi, this is due to inconsistant trigger pulls ,releasing the trigger before cycle complete.
this can cause the semi auto lever in the gearbox to settle in the wrong position after a shot and either jam the trigger or open circuit the trigger switch stopping the gun from working, a quick full auto burst will cure this.
but as above i find nimh cells unlike nicad dont slow down they just go flat, and if the tappet nozzle is in the correct position pulling the trigger can rock the gearbox between the anti reversal latch positions causing it to multifeed bb,s but not fire as to flat