Hello, I was shooting my M14 this weekend with a box of Hornady Match grade 168gr. On about the 9 or 10th shot I noticed a nice puff of smoke that seemed to be coming back towards me on my last round. Happend to look at the primer and it looked like it was struck super deep.. almost like some one drilled into it with a # 40 drill bit. kinda blackend around the edges.. Is this the results of a bad primer ? or is something else going wrong with my rifle ? I gave it a quick look over, didnt notice any changes. Switched to a box of federal match grade with no more issues. another thing ive observed that probably has been like this for awhile.... But I just noticed now cause i spooked myself. with the bolt fully forward and closed with no round in the chamber theres a little bit of slop in the bolt... I assume this is normal... anyways maybe you guys can help me out