I can't help you with a BP load BUT .....    would like to hear of your experience with WP.  Please send me your loading data for this cart as I have built a "Redfield " in this cal but have never shot it ... haven't even got brass for it yet but will get some from Buff Arms.   Ken ( kenhurst1@earthlink.net)

40Rod;
I am still fairly new at the breechseating thing but based on powder burning rates, if 4759/5744 are indicated, then so will the 4227s. Also possibly Reloder7, though I'm not sure I have heard of it being used in a breechseating application. It would be on the slow end of the range of  slow pistol/fast rifle powders and would often be indicated for a cartridge such as the .40-60 Maynard in fixed ammunition. Your project sounds very interesting.

   Hi 40Rod,
                  This is not exactly what your looking for because I use mine for BPRC Sil. and C/B SS matchs but it might help.
Stevens 44 1/2, GM 1/16 30" long. Cases formed f/ 30/40K ,Rem. seems to do best, finished blowing them out w/ 20gr. 5744 and 210gr. lead 41mag  pistol.
Best loads;  60gr. 2f Goex or 58 2f Schuetzen, Rem pistol primer, 2 .030 ldpe wads, 400gr mos/ or 410 Saeco WW+2%.
Tried softer lead but n/g, have not found a load for Swiss either.
Tried 4759 & rel 7, best W/P load 20.5gr. 5744. loose cotton over powder and ldpe wads under bullet base. Rem. LP
                  HTH, John