I DO NOT want to debate the 325vs338 thing, but comparing bullets of similar SD, the BC of the 338 is much better....
that's all.
If I bought a 325WSM, it wouldn't be because I thought it would perform like a 338wm.
325 is a good cartridge for its' own reasons.
I think the new Federal338 is a good cartridge too, but would not compare it to a 338wm.
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If you leave things up to interpretation, there's no room to be right.