Re: .338 Lapua Reloading Die questions
Neck sizing dies are NOT interchangeable between (most) calibers. The bushing just gives you the flexibility to precisely control neck tension and eliminate over-sizing (ie constricting the neck way down then re-opening it on the upstroke like a conventional FL die).
New Lapua brass should not need to be sized, neck or otherwise. Just load and go!
For bushing selection, Redding recommends that you measure the OD neck diameter of a loaded round (in the brass you intend to use) and subtract 1 or 2 thou. I always end up buying 3 or 4 bushings to cover a range, especially if I intend to load using different brands of brass. I'll see what bushing I am using for 338LM (Lapua brand) later today and post it. It will be FYI only, as you will need to make sure your brass isn't slightly thicker or thinner thus needing a different bushing size.
As far as sizing, a lot of guys only neck size for bolt guns. After a number of firings, the brass is difficult to chamber so they use the body die to bump the shoulder back slightly. I personally do this step at every reload as a matter of preference. I typically body size first and then neck size. Not sure it matters...