I have found with one of my M14s, even though it there are no visual signs of a pierced primer, every time I go shoot it, at the end of the day, Imy firing pin is no longer loose in the bolt.I strip the bolt and every time, there are small shards of metal in the firing pin channel. The key is to learn how to properly strip, then re-assemble the bolt.Im not sure where, but there is a link posted somewhere here, if you use the search function, with useful tips on how to re-assemble your bolt.The secret for me was cutting off one coil off of the plunger spring, as it is too long.Now, I am able to re-assemble my bolt every time, in seconds, with-out a special tool or extra set of hands!!