The key to cast bullet accuracy is fit. You must fit your bullets to cylinder throats. Bullets do not need to be super hard either. If not fit properly hard cast will usually lead worse. I cast 310 grain bullets testing 15 bhn and push them with H110. My usual 45 Colt loads are HS6 or 4227 for 1000-1100 fps and are cast from 50/50 pure lead/wheel weights with 2% tin. Lube plays a big part also. Most commercial cast bullets contain hard lube that may not work. Try a properly fit cast bullet of 260 grains on top of 20 grains of 4227 and a Fed 150 primer. Very accurate in all my Ruger 45 Colts. Good luck!
