RL15 was the "magic powder" for me in .375H&H. IIRC, 76 grains of RL15 got me to 2830 fps under a 235gr TSX in a 26" barrel. Stopped there because it was sub MOA to 550 yards and fast enough for what I needed. Current Barnes online reloading manual says that 81.5gr of RL15 will get you to 3,000 fps...

Barnes 375H+H Loads