Hub,
That .30 Carbine Blackhawk is one fun revolver! Had one for many years back in the mid 80's, should have never traded it off! It was great fun on jack rabbits, called coyotes, rockchucks and the like!
I used our .309"-115g FNPB bullets in that little gun, and did it ever shoot! Stoked with H110/W296 that little begger really belched, but shot very, very, well! I took a fancy to Unique and the same bullet to get away from some of the muzzle-blast and fire-ball effect. It worked, but velocities about duplicated a well loaded .32-20. Still great fun, and very economical to shoot. Given today's selection of powders I would probably also try Universal Clays and AA #5 for reduction in the ear-splitting report.
The throats on those guns are pretty tight, and .309" is generally what works the best, use a #10 oval egg fishing sinker to slug the throats in your chambers to determine diameter, then use alloy bullets of that diameter in your handloads for some eye-opening accuracy!
Enjoy, and God Bless,
Marshall