My brother recently bought a previously owned Para-Ordinance P13.45. For thise of you not familiar with it, it's basically a 1911, but it takes a double-stack magazine. Today we took it to the range to test it out. It started fine, but near the end of the first magazine it fired 2 rounds when he only pulled the trigger once. We weren't sure at first that this happened because we found a live round behind him. We thought maybe it ejected a live round somehow since stranger things have been documented. That magazine finishehd out without incident.
I had the 10-round magazine loaded to try it next. Insert magazine, chamber a round, pull trigger, bangbang. Black rifle guys were reloading at the time this time, so second bang wasn't them. I ejected the magazine and emptied the chamber and the magazine into my hand. Look where brass has been ejecting, 2 empties. I reflect that the recoil seemed to lift the gun higher than expected.
So, what is likely happening? The gun inconsistently shots once and twice. Is there anything we should test to help discern the problem? I was thinking maybe load a few magazines alternating live rounds and dummies so it can't fire twice if it wants to, but we can tell when it would have.