I had a 223 bolt head removed and a 308 installed. When I went to load a round, it would have a very light firing pin strike. Turns out the ejector tab was hitting the chamber walls and not allowing the round to seat all the way down, thus spacing to far forward to hit the primer well. He trimmed a couple of thousands off the ejector tab and now the shell seats all the way and ejects right.

Hope it helps.

Larry
Tinkerer