Was shooting my Gp100 today. I had 4 rounds left, so I randomly loaded two empty shells and spun the chamber to see if i was flinching (I wasn't). Cylinder only turned halfway and then locked up. Opening the cylider and removing the cases got it running again. The empties were mine, but I picked them off the ground. Any idea what could have caused it? I cleaned the gun when I got back and it functions fine.