I am using 4759 and Unique in 45/70 and 40/65. I find both burn relatively clean. I have very little experience with the 40/65 though.
My Unique loads run in the range of 12 to 14.5 grains with all bullet weights in the 45/70.
My rifles are Brownings and are too difficult to dissassemble for use of BP
for me. I might try black powder with a RRB but I am mostly too lazy and concerned about a rusting everything touched by the BP.
I would like to hear from anyone that uses light smokeless loads at about 1100 to 1400 FPS. If anyone has any bullet or powder recommendations I am all ears. I am also interested in mold recommendations for 300 and 405 grain GC 45/70 bullets and a light 260 to 300 grain GC bullet for the