Hiram,
You will find that 64 gr of Swiss 1-1/2 will get the same velocity of the original BP load using the 500 gr 1881 (NEI) bullet. You'll also discover the accuracy is far superior to the 3031 load, or any other smokeless load. Trust me I've tried all the smokeless stuff. I get sd's of 4 with BP and a SOLID 2-3 moa at 400 yds. The old warhorse won't come in much better but it is very reliable. 3031 powder has click fire igntion and will not bump up your bullet. Get back to the black.
TL