I tried the search option, but didn't really find anything in enough detail or that helped, so here goes.
I recently got an Echo 1 mp5 with a version 2 gearbox. When it's on single fire it shoots fine, When i swap it to full auto and pull the trigger it works, but as soon as i let off, the trigger won't pull anymore. It is locked up.
I've taken the box apart, and what i can see is the trigger block is going back too far and not lining up again. It gets cocked at an odd angle. But i have another block and compared the two and didn't see anything out of the ordinary. Nothing broken or missing.
I can however dis-assemble the gun down to the gearbox, release the anti reversal latch and it works again until i go to full auto and release the trigger. Then the trigger gets stuck again.
When it happens, the piston is in the furthest back position also.
Does anyone know what could be causing this? The tappet plate looks fine (the little grooves that the block sits in) the gears are ok. I'm just lost on this one. Even the selector switch thingy looks ok.