The fastest burning powder I have used in my S&W 629-3 (4" bbl), with a 260 grain plain base home cast bullet (wheel weight alloy) is Green Dot.
I don't have a standard load yet, as I picked up a bunch of powder from a known (trusted) reloader, and he had several open bottles of powders to play with (before settling on "one load). All the following worked fine for me. I normally stay below 1100 fps, and more typically load for 900-1000 fps ( "moderate" loads).
Powders tried in my S&W 629-3 (4" bbl ) include:
Green Dot
Unique
Herco
Power Pistol
Blue Dot
800x
Green Dot was a nice surprise. There wasn't a lot of info on Green Dot and the 44 mag online, but I did find one reference that it was a secret accuracy powder of Hercules' technicians for light-moderate 44 mag loads. Don't have the load handy, but it was supposed to be around 875-900 fps (no chrono), with 260 grain cast bullets.
I'm glad Green Dot worked well in my pistol, as there was one partial 1 lb can, and two unopened 8 lb jugs of it.
Hp38 is essentially the same as W231. My take is that they are faster burning than Green Dot. You may want to give HP38 a whirl, since you can find it locally.
