I spent the best part of one summer loading 45-70 foe a handi with Goex 2f and various cast bullets & primers,wads.disk. exc.
A great learning experience. But very time consumming and the 22 inch Handi barrel imo is too short to fully use the bp.
I returned to my plinking load that was a moderate load of imr 3031 and 405 home cast. these were quick to load, cheap and 1.5" groups @ 100 yards.
I'am not done tring BPRC by any means, but hope to do it with a proper rifle next time. Besides I love shooting the 45-70 its a wonderful cartridge!!
Your luck may vary from mine, give it a try if you have the time you will learn alot about powders, bullet casting and lubes exc. all of which will make you a better reloader bp or smokeless.