That's entirely normal for warmer ammo. hotter ammo ejects more positively, and so dents more deeply on hitting the deflector. If it was an older model without the deflector, the brass would have probably dented on the case mouth itself. Most of the dent will come back out on sizing. what doesn't come out on sizing will pop out on firing. If you think that is a dent , you should see what happens to .308 brass in a Galil. Those puppies almost get folded in half.