I'd suggest slugging the bore. Some years before moving to Alaska I'd bought an Italian made (Pedersoli?) Sharps 1859 New Model from Navy Arms, and borrowed a Lyman mould from a friend who cast bullets for his original Sharps rifles & carbines. The mould cast something in the .545 range as I recall. My Sharps slugged at .52 or thereabouts. Turned out Dixie had the proper projectiles, as well as the nitrated paper for rolling the paper cartridges.Now I have to save up the money for a mold. Not many people make them and they are pricey.
A friend loaned me his 45/70 a couple of years ago for a competition, and I won the championship. I used his 45/90 last year, was sighting it in during the competition, and lost by 2 points. Long story short there. I like the guns; satisfying to shoot, but need to learn how to absorb the recoil better. It goes "bang" and I brace myself for the "OW" about a second later.Nice I love my Sharps 45/70