I'll post this here since technically this thing is a pistol. This is only the second time I've taken the MPX out. The first time it had the icky stock trigger. I installed the Timney one a couple weeks ago. It started double tapping and I only got about half a mag through before the range officer made me put it away ASAP. Anybody have an idea off the top of their head what would cause it to do that? Perhaps the set screws weren't tight enough? It's a drop in unit I don't know much that's there to mess up.