So we loaded up the new .375 GMX bullet the other day for my 375 H&H that there is no load data for yet, so it was a bit of a guessing game. Anyhow, ended up with a 250 grain bullet going 2810fps with no pressure sign at all and putting three shots touching at 100 yards was no problem. It seems a bit hot compared to other 375 loads....what kind of velocities are others getting out of 375s.

With the 250 gr Sierra GK out of my .375 H&H, I am getting 2820 fps, excellent accuracy and weight retention of 75-78% on big game like Eland at 85 yards. But that load is right at max velocity for the gun/bullet. That bullet probably produces less pressure than the Sierra so I wouldn't be concerned if you are happy with the load/accuracy.

Ya not sure how it would compare in pressure.....the GMX is longer for sure but the two cannelures definitely help reduce pressure. I'm thrilled with the load and if this bullet performs anything like its smaller calibre cousins, it should be an ideal dangerous game choice with nearly 100% weight retention but still 2x expansion.

My favorite load for my 375 H&H gives 2760 fps from my 24 inch barrel. This is with a max load of H 4895 behind a 270 grain Barnes TSX.

So, I would imagine 2810 fps with a 250 grain bullet would be reasonable.

Bullet weight makes a lot of difference in the 375 H&H. My best loads using 300 grain bullets run about 2550 fps.

Almost 20 years ago, I loaded up some Barnes X 250gn bullets in my 375H&H for a planes game hunt. At that time, I could not find any data on this bullet, so used loads for a 270gn bullet as a starting point and loaded looking for pressure signs. Using Varget, I got that bullet over 2900fps without any pressure signs, but stopped at 2900 as it gave me the best accuracy.

I took 8 animals with the load, and found it worked very well. I left my ammo with my guide after that hunt, and was told later that another hunter used my ammo in a rifle borrowed from the guide for a 1 shot stop on a cape buff.

Sometime later, the 1st Barnes loading manual came out, and I looked up this bullet out of curiosity. I was quite surprise to see I was operating some 200fps over the recommended max load/vel.

.375 Wby / 250 grain TTSX / 2825 fps
(max. H&H loads are good starting point for Wby, so I'd stop where you are)

I haven't shot any bullets out of my .375 H$H lighter than 300 grains.
With 300 TSX's and 300 Partitions I'm getting 2602 fps average.
Load 71 grains Reloader 15
Rifle is a Win M70 Classic Stainless 24" barrel.
Typically shoots TSX just under 1" at 100 yards, best group 5/8".

2780 fps in a Mark V 375 H&H with the 260 grain Nosler partition. Your velocities seem very much in line with a bullet 10 grains lighter. And my load was 1/2 grain under book max for that powder.

Loaded 300 grain A-Frames a couple of years ago for a buffalo hunt and got 2550.

Hopefully this gives some indication of what's reasonable.