Have you tried Alliant Unique? It works well in straight walled cases. My old Lyman 45th edition has cast bullet data for the 45-70 and 458 winnie. I generally load 16 grains behind the Lee 405 grain in the 45-70 and 21 grains behind the Lee 500 grain in the 458. I haven't chono'd these loads but both should be going 1300-1400 fps. The 458 is a Ruger no1 - obviously no feeding problems. But I sometimes load the Lee 500 grainer in a 45-70 Winchester 86. Again no issues, flows like water through the rifle.
These are not compressed loads in either cartridge. Also, Unique doesn't require a wad to hold the powder charge in place as some powders do.