Very well put, 50Calshtr. Bravo.

Both my brother and I had .45 3 1/2" rifles long time back & it took us 8 years to find loads that would shoot in my bro's Shiloh M74 Sharps. My rolling block in the same chambering was a littler better with it's Richard Hoch barrel.
After reading Paul Mathews (now passed) we tried undersized paper patched bullets with black powder, patched up to bore diameter(not groove dia.) and bingo, terrific accuracy in both. They did both shoot well with jacketed, running 1,600fps with 500's and 2,260fps with 300's. Those bullets also shot well in my Bro's rifle with black powder, no wiping, just shot after shot. He made multiple 'groups' at 100 yards, that were cloverleafs, with both weights.

Of course, both of those sets of ballistics can be easily achieved in a .45/70 with smokeless powders. The problem with the big case, was space. Too much space that had to be filled with either black powder or wads, or now, we learn, foam backer rod. Nothing was really gained over a much shorter case, though, except when using BP.