What is the opinion of a 338 Lapua necked up to 375. The water vol is 108gr or just a litle bigger than a 375H&H AI. This is a simple conversion with plenty of power for Buff with solids.

wasn't the .338 Lapua based on a outblown and necked down .416 rigby?

if so, shouldn't it be roughly the same as a .378Wby

Probably similar to a 375/404 Jeff. But if its close to the 375 H&H AI....then its also very similar to the 375 JRS, 375 weatherby, 375 Dakota, but with less capacity then the 375 RUM or 378 Wby.