Not sure exactly, but with heavier bullets in the 250-275 weight range I used RL22 and similar for the top speeds, I’d kinda think you’ll be using faster powders in the 375 version with the same bullets. It’s quite a lot different in diameter. Kinda like the 06 and 35 Whelen. There is some crossover but not a ton.
Maybe check case capacity and see where you sit compared to the 375 H&H and Ruger cases and extrapolate data from there.
I’d think minimum H&H loads would be a place to safely start and you can adjust from there as needed.
