JAT - Hornady's 9th edition reloading manual shows both .458WM and .45/70 Ruger #1 info. Loads for 350gr.RN show several useful powders (H4198, RL7, H322) that cover both rounds. Hi end .45/70 Ruger #1 recipes that overlap the
.458WM's starting loads is a good place to begin. You don't need 500 grain loads for white tails... Have had fun with un-sized .45 Colt lead slugs (single loaded approx. 260+ grains), on a whim, hunting the local swamp bunnies. No danger
of a crazed "charge" here but great fun none the less. "szihn" remarks are very similar to my own experiences. Homesteader
