I had a bad weekend with the su16. First the it kept stove piping. And double feeding. Then it started shooting really low. Like into the ground. I was shooting a gong about 75 yards away. And the rounds shot about 50 yards into the ground. (Red dot was on tight) Then the bolt group got stuck about half way in its track. It would move slightly about and inch back and forth but not easily and I noticed plastic chips/strips on it. At this point I decided to pack it up. The screws in the receiver on top and below the mag release were loose. My uneducated opinion is that maybe the two halves loosened up and the BCG came of its track. I stripped it and noticed more plastic shredded off. Did a cleaning and didnt notice any parts broken. I reasembled and it seems to function fine. I also loctited those two screws. You guys have any idea what happened? Federal brass cased 556 and LaXammo new brass 223.