If you notice that the primers on cases are slightly marked by the firing pin, this is a normal condition for ARl5/ M16 type weapon systems due to the lack of a firing pin spring in the design. This is part of the reason that mil. spec. parts are necessary to ensure safe operation - and we urge you to have that muzzle pointed in a safe direction when checking your rifle in this manner. MIL-R-63997B (AR) states in part (section 3.4.2) "Firing pin indent - when in a vertical (muzzle down) position, the bolt carrier assembly is released from the full recoil position and the firing mechanism is not activated, the firing pin indent shall not be more than 0.008 inch". Also, we sell a firing pin protrusion gauge that will tell you if your pin is within specifications.