If one wished to create a loud, flashy, but low-powered round for these handguns, would a slow rifle powder be safe to try? A friend of mine has a 44 Magnum revolver, and is currently looking for something in 500 S&W. He also has a bunch of pull-down 50 BMG powder (I am not sure which powder specifically), for which he presently has no use. I'm still not the most experienced reloaded, but if I under any of this correctly, excessive pressure shouldn't be the potential issue; just the opposite, in fact. That being said, if the projectile leaves the barrel, there should be plenty of burning powder flung downrange.
Any thoughts?