Phil,
In addition to knowing the bore diameter you will also need to know the rifling twist. If your rifle has a sow twist similair to the originals you will be limited to lighter bullets - probably under 300 gr. A fast twist will accomodate the heavier bullets and make the riffle more versatile.
Started loading for an original 1895 Marlin .40-65 prior to cases being available. This rifle, as would be expected, has the slower twist. Cases are reformed and trimmed Remington .45-70 and the bullet is the 260 gr. Lyman #403169. Both IMR 3031 and Reloader 7 have worked well.
Bill
