Our dept. AR mechanic isn't available, thought I'd ask here. The weapon is a Colt AR, recent A3 type, 30 round GI mag. An officer who used an issue AR on a call the other day handed it to me to clear and put away, his hands were full. When I cleared it, I found that the round he chambered had a very light dimple on the primer, like the firing pin had gone forward and VERY lightly hit the primer when the weapon was charged. I aint no gunsmith, but this looked odd, and I have never noticed it before in my limited exposure to this gun. Cause? AD when charging likely or possible? Normal?