here's another failed piston causing a lockup within the cylinder. no operator at fault, just the normal failure on a hi rpm kwa m4. btw, this kwa is really nice (magpul furniture and madbul noveski RIS). sorry no pix on the kwa yet since it's in pieces at the moment.
problem: no fire when trigger pulled on semi-auto or full auto. i figured it would be a simple electrical open circuit. the L-shape lip broke and rammed the metal (teeth)strip into the plastic head spacer causing it to be at an angle and wedging itself against the cylinder.
diagnostic: simple test, opened motor cover, pull trigger and motor spins when not meshed with the gearbox, therefore, gearbox is locked up.
cylinder wall is scored. this will rip any new piston head o-ring.
that modify re-enforced piston is starting to look like a good investment.
-a|ex
edit: the more i think about it, the least likely the broken lip caused the damage. the piston head was loose when i removed it. methinks the screw loosened up and the head wedged causing the lip to break.