I am at the office right now but I believe I have been using a .366 bushing. I haven't seen any out of round case necks in any Lapua brass that I have, which is why I always recommend Lapua brass. The neck wall thickness is extremely consistent.
Because of the above I do not neck turn Lapua brass.
The Gold Medal set includes an expander plug for new brass that has a dented neck from handling.
I just looked and Midway does expect the Gold Medal 338 LM in stock middle of March. They are however $8 higher than buying them direct from RCBS.
My 338 Lapua is a Ruger #1 that I rebarreled with a Pac-Nor Sendaro 28" (30" w/ brake) barrel. It came prechambered for the 338 Lapua.
I had Kregg Slack install the muzzle brake.
Sightron 6x24x42MD scope.
Brake doesn't show up well in the picture.