Re: IMR 5010 is good for 338-378 weatherby or 264 win mag
Since you're not getting much response to your thread, I thought I might chime in here. You are correct in that 5010 will work well in a .264WM. I am away from my home right now, so I can't provide any loads, however, old Speer manuals do have loads for 5010 in the .264. A newer powder that seems to work well with 140 gr. pills is Ramshot Magnum. Also, H870 is discontinued, but Hodgdon has just introduced US 869, which might be able to replace H870, but is supposed to be cleaner and more temperature stable. This information applies only to the .264. I don't know anything about the 338-378. Good luck!