[Swatt Six-Four]

perhaps your motor lash has been cranked too tight, thereby locking your motor. Just a guess. If you could perhaps give a slightly better description of exactly whats happening it would help. For example, I was working on an M4 someone droped off at my house, what would happen is when trigger was depressed I would hear a slight thump, I would also feel a slight knock on the left side kinda of. When I inspected I found that the motor lash was cranked too tight. I cranked if off all the way then tightened it in increments till gears were meshing properly. My advice would be to back motor lash all the way and see if the motor activates properly. Atleast that would eleminate the fire selectior, trigger mechanism and the motor as the problem. Tighten it in a little bit at a time see if it fixes the problem. Hope this helps a little