My .458 is also a Ruger No.1H. Most useful all-around powder is H4895. It can be used for reduced loads or top loads for 500s. H4198 (not IMR) is best for 250gr to 350gr. And as JPW475 has said, A2230 and 2460 are great performers for 400gr - 500gr.
The big advantage of the Ruger No.1 is its long throat (all .458s) that has no magazine to restrict COL. A 450 - 500gr TSX can be loaded to 3.78" (crimped in the bottom cannelure. I don't always crimp - it depends on the bullet, but most loads are seated long. The 300gr TSX is crimped into the bottom cannelure for a COL of 3.25". Seating "long" leaves more room for powder space. . . in fact, in many cases (pun intended) more than a Lott. The 250gr MonoFlex (Hornady - not the 325 FTX) is a tough bullet made for the 1895 Marlins and single-shot .45-70s, but it's a great bullet in my Ruher No.1H. I push it at ~2700 fps from 65 grs of A5744, and that's far from tops, but it's accurate and good for anything to moose. Etc.
The best all-around load is the 404gr Shock Hammer at up to 2550 fps using any of the best powders for heavier bullets, like H4895, 2230 or 2460. Some newer powders also work well. Anything good in a .223 Rem will work well in the .458. Go to the .458 thread on Express Rifles and Big Bores Only for enclyclopedic knowledge and information.
Bob
www.bigbores.ca
