Nick, With a heaver bullet, (386gr), I used 22 gr of IMR 4198.

I also used a 250 gr bullet, still with 22 gr of IMR 4198. This second load seemed very mild.

I did not chronigraph these loads.

I have not used 5744 that much but see internet comments about using 26 gr pushing a 405 gr bullet in a 45/70. Cast Boolets Said Lyman 51 has the data you want. The Trapdoor loads with a 535 grain boolit run from 23-28 grains.

If I were loading for my rifle, I would probably start @ 23 gr and work upward.

Other people may have better ideas. I suggest you do more research.