I’ve used a Lyman gas check design, don’t recall the exact number on the mould, but it’s around 280 grains. Shoots very well with IMR 4227 up at around 1700 fps. I shoot a very good load on my 358 Winchester with 4759 and I imagine the 375 would also should fine. A simple hard slug pokes a very lethal hole through lowly critters like caribou based on a the heavy M70 375 I’ve used.

Sometimes, the air you 'let in'matters less than the air you 'let out'.