Firing pin protrusion will be the same on all rounds. If you have 2 out of x with shallow indentations, the cause is likely the hardness of those primers, and not the firing pin.
AR 15 armorer manuals use a guage with a GO dimension of .036" and a NO-GO dimension of .028".
With the firing pin held firmly forward in the bolt, the end of the firing pin protrusion gauge (or gage, if you prefer) marked "MAX" (GO - 0.36") should pass over the end of the pin without touching it, and the end marked "MIN" (NO-GO - .028") should hit the end of the firing pin and not pass over it.
What we have here is... failure- to communicate.
Last edited by c3shooter; 09-05-2012 at 12:44 AM.