I have an old Lyman cast bullet book and it shows fast burning powders for the 32-40. The list shows Red Dot, 700X, Green dot, PB, and Unique. I have used Unique in 45-70 many years back and like it. Book shows a max for the 32-40 of 8.5 grains Unique and 164 grain cast at a velocity of 1315. For a short contender barrel the faster powders may be better.