I would say that the 300 grain bullet is the one most likely to give the best and most consistent accuracy with the 375 over a wide range of powders, especially the 300 Hornady round nose and the 300 grain Sierra.
The 235 Speer can be accurate but also inconsistent and far more likely to throw shots from either cold clean barrels or barrels with cold hard fouling.
The load that I have found to be the most accurate across a large number of accurate 375s has been around 78 grains of Win 760 and the 300 Hornady Round Nose.
The powder that seems to give the highest velocity in combination with good accuracy across a wide range of bullets is Reloader 15. That would be the powder I would first choose for the 250 grain bullet.
Mike
I've just gotten hold of some VV 160. Looking at its relative burning rate, it also should have potential in the 375 H & H.
I have very good results with the 250 grain Swift A-frame and 250 grain Sierra with 72.0 grains of IMR 4064 and CCI 250 primers in Winchester brass. This works in all my 375 H&H rifles, but work up from below in your rifle to be safe.
Good shooting,
Jim
I'm convinced they work perfectly, that said I am still a 300 gr. believer..I don't like collecting bullets, that means they didn't make two holes and I like two holes.
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Ray Atkinson
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Gerard Schultz
GS Custom Bullets