They must be some tough or short primers. I can only recall one failure to ignite primer in 40+ years of shooting. It was factory ammo. So I am not really qualified to opine. I've always treated primers with care. The picture provided looks like it is more than just a dent to me.If the firing pin is using energy to push the primer deeper into the case, or its using energy to push the case forward there will be a dent just like what you are seeing, but no (BANG)