Heavy bullets are all the rage in big bore revolvers these days. Ever since the .454 Casull and the .500 S&W Magnum arrived on the scene, the desire for heavier slugs has really come around. You can buy up to 700 grain bullet loads in the .500 S&W today. For handloading heavy slugs in both the .454 Casull and the .500 S&W I use H-110. It is a very fine grained ball powder. It meters very well through a rotating drum, micrometer adjustable measure like the Redding and the Lyman 55, but can cause issues on the Dillon sliding bar type measures because it is so fine it can bind up the powder bar. But for launching heavy bullets out of big bore revolvers it can't be beat. Just be sure to use Magnum Primers and a very heavy crimp. This stuff is hard to ignite. Bill T.