Funny 9mm primer


I picked this one at my club’s range. Why is there a small rectangle in the middle of the primer?


That’s a cartridge case that was fired in either a Glock, or in some versions of the S&W Sigma; all Glocks are produced with a rectangular firing-pin hole, while some Sigmas (depending on when they were produced) have the same distinguishing characteristic. The bright spot out on the edge of the primer pocket (towards the dash after PMC) is an ejector-mark.


ooops, I was too late and repeating what has been said already.