I know I am probably beating a dead horse with this one BUTT:

4.5 - 5.0 gr PB with FILLER (you pick: grex, used polishing
compound, etc.) and a 240 SWC.

This has never failed me in both .44 Special and Magnum
cases. All holes touching at 25 feet.

Shot this in 6" 629 and all 3 624's. Works.

Takes some extra effort to load and is a minimal (700 fps)
load but I guess I lucked out with my bores.

PB is an overlooked powder. Extemely clean.