Sharps Nitro - I've done the same thing but on a strong rolling block, but went to the .45 2-7/8" case. That's about max for easy loading with smokeless. The 3 1/4" cases are a pain with today's smokeless powders. Even a .45/90 (2.4") with a 3/8" leade and 2 degree throat will give identical ballistics to a .458 WM on a Ruger #1.