It will open up real good at 750 fps plus so you are on the right track. I would start with 8.5 grains of Unique. The 250 grain Gold Dot at 775 fps will penetrate 14" of ballistic gelatin and expand to .773" - The would be an A+ based on the FBI standards.
From Shooters Legacy site article by Gary W. Campbell 6-4-08
http://www.shooterslegacy.net/articles/45colt.html