Light Primer Strikes on Chambered Rounds

This is completely normal and is a characteristic of all basic AR15/AR10 rifles. The firing pin in an AR15/AR10 is free floating inside its chamber. The forward inertia of the bolt upon chambering a round causes the firing pin to bounce forward with just enough force to leave a small mark on the primer. This is never enough force to cause a slam fire.  Cycle chambered rounds as a best practice.