18.0 to 19.0 grains of IMR4227 in a .45 Colt case behind a 250 or 255 grain cast bullet is a good load in a S.A. Colt clone, without stressing them out. I've also 4227 with cast bullets for a .444 and .45/70 rifle; which works great for plinker loads, and is satisfactory for close range deer hunting. I believe Hodgdon's market both IMR and H4227 showing powder load recipes as being identical.