Using soft lead over BP, you may or may not get leading and poor accuracy with a .427 bullet. Just have to try it. Handguns tend to be a little less forgiving, I think, than rifles when using undersized bullets. But then BP is known for "bumping up" soft bullets.

Your 44/40 dies will not work. The 44/40 is a bottle necked round, with a cartridge base diameter of .471. The 44 Russian has a base diameter of .457. If anything else (never tried that die / caliber combo) you would not be able to resize your Russian brass. Maybe a cheap Lee loader (the old hammer kind)? I noticed the other day Starline has .44 Russian brass in stock.

Larry