Ok, I have the redding deluxe die set for my 338 lapua and it comes with a neck sizer. I followed the directions that came with the die set for setting it up. Never really neck sized anything before. Ran a piece of once fired brass through it and took some measurements and was left scratching my head....inside dimension of the case mouth is now .350"! I can't afford to be screwing up Lapua brass....so what the heck is going on? What am I missing???