27 January 2009
For what it is worth, my favorite load at the range in my .375 H&H Remington 700 uses the RCBS bullet (265 gr. with wheelweights and Hornady gas check), 24 gr. SR4759, and WLR primers in W-W cases. Velocity is between 1500 and 1600 by interpolation, and accuracy just keeps getting better. The throat has been tapered a bit so it might be more like the Ruger.
I measure SR4759 instead of weighing it, so sometimes get a light load. When the SR4759 is gone I will try 2400 because of your report of using it in the .22-250 (and having a lot on hand), trying 20 gr. to start. I have used SR4759 in hunting loads at 2,000 fps, but I will use H4895 after the present hunting rounds have been used up. In FS 94-19 (1991) Jim Wilcox of Vale, OR, reported very good results with 45 gr. IMR 3031 in his Winchester Model 70 using the Lyman 375449 cast 1:10. You can interpolate from there.
I use a Lee collet die set with the sizing mandrel turned down to size the case neck more. That holds the bullet well. From time to time I have to resize full length so the cases will chamber.
The .375 H&H is a very nice cast bullet case. And it is fun to see the expressions of the varmint gun guys when they see the cigar-size cartridges. And after all, a hunter with a good .375 H&H really needs no other rifle.