What is the best powder for the .375 H&H?

[S-3 ranch]

I don’t have a H&H but a 375Ruger and my book has a h&h 4350 page

 

[BlaserNut]

Part of what's going on includes how much more "overbore" the case diameter/capacity is over the bullet. I can't really give you the exact science, but in concept the closer they are, like with .308, .35 Whelen, or .375 H&H, the more benefit you get out of quicker burning powders. The more overbore, the more benefit from slower burning powders.

Heavier or lighter bullets in that same cartridge might mean a little slower or faster burning powder, but it's not as big of a difference compared to when you take that same diameter bullet and put it in a really overbore casing.

That's why you generally find quicker burning powders in .308 Win than you do .243 win, or between .308 Win and the big .30 cal magnums. The more overbore, the more benefit you generally get with slower burning powders.

Bottom line: It doesn't matter how big the caliber is, what's at play is a ratio between caliber to case capacity. The closer the ratios between different cartridges, the closer their powder needs will generally be.

That actually makes a lot of sense. Thank you for taking the time to explain that to me. I had always been told that it was Barrel Burn Time that was important, that the best load was one that burned to completion just as the bullet exited the barrel. As I think about how many other variables get introduced into theory, I can imagine that such a situation would create very inconsistent shot patterns. I always appreciate good insight.

 

[BlaserNut]

I've received some good education and feedback. As I have a fair amount of H4350 I'll start there. I've also got a fair amount of H4895, so I'll load a batch with that as well. I'm very curious about how the Leverevolution with perform, so I'll make up a batch with that as well. You've all given me a lot of suggestions I can play with, now I've got to start a post on finding more time, haha! I'm going to have some fun!

 

[Radosilver]

I know this is an old thread but I’ll throw out some info on RL15.5 since there doesn’t seem to be any in any of the load books yet that I’ve seen. I worked up a pretty good load with 250 TTSX and 72.0 of RL15.5. I’m sitting right at 2,700 fps out of a 24.4” tube with very good accuracy and some very low velo spreads. Varget at the same powder charge was faster by about 50 fps but not as accurate in my rifle. I went up to 73.0 of RL15.5 and didn’t see any pressure signs. Didn’t bother trying to go higher as the groups opened up so I just backed it down to the 72.0 the rifle seems to like. Figure the RL15.5 info may help someone out as RL15 is nonexistent but 15.5 seems to be available several places lately.