Question.....Are you FL sizing or neck sizing? Is there a reason, other than to iron out the bent up necks from the factory, to size the brass?? If not, I would NECK SIZE ONLY. I have never used an Edge, so I don't know all of the steps in forming the brass. I assume(:eek
that you are simply necking up 300RUM cases to .338, and everything else happens during fireforming.
I HATE FL sizing anything I don't absolutely have to!!! I have seen this before, but only with FL dies. I have never seen it with a good Neck die with the different size bushings used to adjust neck tension.