IMO, that's common enough to be called normal for the AR platform. It's caused by the floating firing pin. I first saw it in the mid 70's when my grandpa bought the first AR I had ever seen, a Colt SP1. Every AR I've ever paid any mind to did it.
From the Colt AR15 owners manual.
Note1: On Colt 223 cal firearms, it is normal for a light firing pin indent to appear on cartridges which have been fed into the chamber, but not fired.
From the Colt AR15 owners manual.
Note1: On Colt 223 cal firearms, it is normal for a light firing pin indent to appear on cartridges which have been fed into the chamber, but not fired.
