Ruger .45 Colt Blackhawk is a beast. Buffalo Bore Web Site
"Heavy .45 Colt +P - 325 gr. L.B.T.-L.F.N.(1,325fps/M.E.1,267 ft.lbs.) - 50 Round Box. These Heavy .45 Colt +P loads are safe in all LARGE FRAME Ruger revolvers. (includes Blackhawk, Super Blackhawk, all pre-2005 Vaquero, Bisley, Redhawk)"
I'm happy with a 255 grain SWC with 10 grains of Unique.