IMO a 270gr would best the best all around. I have easily attained 2800fps with Big Game powder and Fed 215, WLRM, and CCI 250.
I have been working on loads for my 375 for the last year. I have tried 250 TTSX and GMX, 270gr TSX, Hornady's, and 300gr TSX's.
My rifle does not like the 250's at all.
270's are a little better with an absolute tack driving group at only 2515fps though. Groups open up as velocity/pressure increases. The 270gr Hornady's are no better.
Really likes the 300gr TSX's at 2622 and 2537fps respectively. All powder charges shoot respectively better than all but the above listed 270.
With 2 1/2 months to go, I am going to use the last of my 270's for practice, then start in on the 300's saving the last 60 for the trip.
When I asked the PH what he prefers in a 375 H&H for buffalo, he stated 300gr TSX or A-Frame, whichever shoots better. Will a 270gr work, absolutely, but no reason to not follow his advice.
Your rifle may tell you what bullet to use. As my rifle is a little picky, hopefully yours will not be.
