So the problem is once i put the gearbox it the lower and the upper and insert all the pins: safe works great, semi works great, auto when u pull the trigger it goes back slightly and when u apply some pressure it snaps back (as if you were on safety and then suddenly it gives) and does not fire. However when the pins are not in and only the grip is attached it works fine. So has anyone else had this problem? It seems as if the selector plate is being iffy or not connecting right, but I have no idea why the upper recieve affects it. Both recievers are metal. Is there a certain order in which my gun needs to be assembled? Mods ive done was slightly sand down the bottom of the selector plate so it didn’t catch on gearbox. (The part that floats over trigger contacts.) but that hasn’t reduce the overall length or the contact with the selector switch. The gearbox and selector plate are both stock on the LR300 a&k. Any help would be appreciated thanks!