Re: few questions 338-378wby
Yes . . . and no. Yes, you can neck up the 30-378 brass to .338, but no, you probably won't want to use it "interchangeably" with the other factory 338-378 brass. It may work just fine, probably will in fact. But it's still a different lot (at the least) and is likely to have somewhat different neck wall thicknesses, different neck tensions, capacities, etc.. I've necked up 30-378 cases to use in the 338-378, but I never mixed brass. Keep them separate, treat them as individual lots, and you'll get better results all the way around.