These are new brass chambered just now, the dents are occurring when the round is chambered. It's definitely the rifle and not the brass. It looks a like the right side feed ramp has a wear mark?
Well it must be denting them on the way out too because Shep is completely correct that the dent made going in would not be there after being fired. The pressure from shooting would have completely removed the dent from the loading activity. That and the dent on the fired shells looks to be quite a bit bigger than the ones on the chambered and unfired rounds. At least you know where the damage is coming from now.