KInd of politically incorrect to be shooting smokeless, GC loads in a Sharps but just trying to broaden the possibilities.
The easy one is the 45-70 by staying with trapdoor or lower pressure levels. The tricky part is going smokeless in the longer cartridges like the 45-2 7/8 or worse yet the 3 1/4! While working on the 45- 2 7/8 with the chrony I noticed that even with the smokeless powders that are listed as suitable for or should NOT be case position sensitive I was getting all the signs that the long case with the smokeless WAS
showing squirrely SDs and velocities. That includes a load that I know is used by one of the commercial loaders and is listed in a couple of manuals for 45- 2 7/8 smokeless. May or may not be a problem but I sure payed attention to it. I read the chrony data as a warning.... not to mention that for any accuracy at extended ranges it simply wouldn't work. One of the best powders for this type application seems to be 5744.
BTW, I do shoot a lot of BP loads in both the 45-70 and 45-110 (2 7/8). The 45-70 is a Shiloh and the 45-110 is a C Sharps. The 45-110 (2 7/8) really likes swaged paper patched bullets over BP.