I used mostly 270 and 300 grain bullets for the largest part of my shooting with my 375H&H and I have fired it so much in the last 44 years I had to re-barrel it because I shot out the throat on barrel #1.
The powder I found to give me the very best results overall was IMR4064.
The 10 grain lighter weight of your bullet would probably not make a lot of difference. Might try 4064 and see.
Yup, not a surprise. IMR 4064 has worked very well in many cartridges. I read that, at one time, the .375 H&H was factory loaded with IMR 4064 powder.
RL-15 has become such a popular .375 H&H powder, one wonders about similar burn rate powders if and when RL-15 becomes hard to find (like now).
In addition to 4064, Pw Pro 2000 and CFE-223 are close, as is Leverevolution and the now discontinued 4320. Also Vv n-135 and Norma 203B. So, in this day and age, you shoot what you can find. Seems about anything in that burn rate range may work. The old .375 H&H is pretty versatile.
DF
