Yep. beat me to it Tom, I think it ends up around 75 grains but figure out what you and your rifle are happy with specifically.
That 270 is a magical projectile in the 375HH. Lets think back to the original 375 loads for both speed and weight 2400-2500 was typical at 300 grains with a bullet that was not always stable and often crumbled. Even the FMJ bullets we often failing.
The 270 TSX does not go to pieces, might lose petals but the mass will continue to drive through, and drive through straight. With the brilliant reputation the 375HH had, now imagine what it does with this load. Think back as well to the original 375 Weatherby magnum, not the current Weatherby but the original. That rifle was an overwhelming popular and supremely lethal gun on African game. However the bullet was still the weak link.
Now with a 270 grain TSX you can transform your standard 375HH into something even better then the original Weatherby version. It will shoot a 270 TSX at 2800 or a bit more. Using a bullet that will handle impacts at that speed flawlessly.
The 270 TSX in the 375 is the perfect match to this cartridge. One thought that we collectively need to get though, be aware that all rifles are different. Make sure your cases come out easy and cycle flawlessly. Don't risk 2850 to struggle with feed, extract issues. 2775fps will function just as well on soft tissue! Cycle every round through your gun before you take them into the bush.
My rifle shoots 2850 very nicely, however I eventually settled on 2800 for safe and reliable function in my model 70. When nearing the maximum levels small amounts of powder get you to trouble quick!
I can second this but used H4350 and at a little slower velocity--~ 2700 fps. It was unbelievably-to-me accurate. And took all the PG with one shot.
