I have been a lurker on this and other boards for a little over a year now. I have had an import 45/70 sharps for about 30 years and tried unsuccesfully to get it to shoot for the 1st year or two and then gave up.
After discovering the various BPCR forums on the net in 2004 it gave me impetus to try to load for this rifle again, long story short. I have tried various techniques, bullets, and material and have finally found a load that works for me. It only took a year and 50 pounds of lead, lost hair, fingernails and lots of patience. I know I'll hear plenty of catcalls about this but I am unable to find Goex locally and can't justify buying 25# at a time on the net, my load is 43 gr. by whgt (55grains volume) of 2f T-7, with a Lee .459 405 HB (416 gr. with Lead) this load is giving me 1344 av. velocity with 6 SD. I can shoot 5 shots from a bench into 1.25 groups at 100 yards consistently.
I took the Sharps with me to Nebraska on my annual Muley hunt in November and was fortunate enough to tag a 5X5 with a 24.5" spread on the first morning. The shot was 225 yards, bullet went in just behind the near shoulder and smashed the opposite shoulder, I found the bullet just under the skin on the opposite side with very good expansion. This Deer went about 90 yards. This isn't my biggest Muley but it is the most satisfying because I got it with the 45/70 and open sights.
Got back to Michigan and went Whitetail hunting & shot an 8 point ( Eastern count) that was facing directly at me in the brush, I held just below the throat patch and dropped him in his tracks at 75 yards, the bullet went completely through the Deer lengthways!