I just got a preban ar15, colt match hbar lower, the upper doesn't have any markings so I'm not sure what it is. The problems I am having are the bolt doesn't stay open when the mag is empty, that's annoying but no big deal, the main problem I am having is when I put the mag in and hit the bolt release it doesn't push the round into the chamber it gets stuck. This only happens on the first round of every mag, it cycles fine when its shooting. one last thing, last time I was shooting it one cycle felt rough so I popped the mag out and the top round had a dent in it about an 1/8th of an inch deep and a little over a half of an inch long, this only happened once. can any one tell me what would be causing these issues. Any input would be greatly appreciated.