The StaBall 6.5 seems like a pretty good idea as far as powders go. Don't think I have seen any 458 loads with it, but it looks good for .375H&H. In mediums, I also like 350RM and 9.3X62 and I don't think I have seen it there either. I will admit to not understanding powder very well. Why would a powder be good in a small case like 6.5C, as well as 375 H&H, but not in something like 9.3X62, or 350RM?

Sounds like it would not be good in 458 either, lol. I'm just looking for more universal powders still, as Varget seems to be impossible these days.