The other day my Borden tube gun (.308 Winchester) action *almost* pierced a primer. It got pushed back to flat, but didn't get punctured. I heard a ping, and the shot went 5-7 MOA to the right. After that, the point of impact dropped about .75 MOA, and it went from shooting in the .2s - .5s to no better than .75 MOA, with several three shot groups between 1-2 MOA. I haven't tracked down the reason for the primer mishap. I'm going to double check my dies, but I'm 99.9% that they're sizing .002. This was primer number 800ish out of a box of 1000 with no issues. The load was hot, but not the highest I've shot through this rifle, even on that day. I pulled the bolt apart. There is nothing obviously wrong. Since the primer didn't actually blow, there's no primer disc floating around. A dial indicator on the firing pin shows that it runs out .005-.007" at the tip (the fat part of the pin is .001"). Jim doesn't think that's the problem. The trigger is a CG two stage. I pulled it apart and nothing is broken. The cover plate screw was slightly loose, but I'm not sure how popping a primer would cause that. The drop in accuracy/change in impact was immediate and significant. Before I just give it all a thorough cleaning and put it back together, is there anything else I should be looking at? Edit: None of the obvious stuff was loose - scope rings, action screws, etc.