I have an AR that I keep in my safe on hot ready to go. Every so often I will rotate mags and pull the chambered round and set it aside. Today while doing so I noticed a small indention like a firing pin hit on primer. I looked at the last round I put aside and bingo it had the same thing. Not nearly enough to fire the round but an indention thus the same. Is this normal? Do I have a problem that I need to get fixed?