Quote Originally Posted by GtownGeorge View Post
Thanks for the responses. This is a new rifle with less than 200 rounds. I have shot several different 'cheap stuff' with no issues. I have checked out the firing pin etc and it doesn't appear to be the problem. Must have gotten some really hard primers.
I have seen Federal 5.56 M193 cases .009 shorter than a GO gauge, I would measure some new cases and fired cases with a Hornady case gauge. A firing pin at minimum protrusion and a short case shoulder location at minimum SAAMI specifications could create excessive clearance between the bolt face and the rear of the case. Combining excessive head clearance and a hard primer may be the problem.