I've got a 338 rem ultra mag in which I have reloaded for and had 3 primers develop a pin head sized hole in the edge of the primer melting some brass as well as the some of the face of the bolt, these are Federal 215m primers. these loads for this gun are below max and show no extraction difficulty. I suspect the age of the primers may be an issue, but the age is not known at this time(a friend of my son gave him 5000 primers) but am not certain. I'm using new Remington brass . Does anyone have any ideas what would cause this to happen?