Both of my BH 45 acp cylinders have been reamed by the cylindersmith to .4525. Prior to reaming I could not get either a lee 252 swc or a lee 255 rnfp to chamber at reasonable oal. After the fact they do ok. In the BH 45 acp cylinder:
lee 252 swc LA tumbled air cooled sized .452
cci 350/ winchester large pistol primer
6.2 unique
oal of 1.20 (just onto the front band)
taper crimp to .469

Actually shot pretty well out to 25 yards in the BH. I even ran some through my Rock Island officers model 45 acp (until I got worried about battering the little 'Rock") i do not have a chono so no idea what it was running . based on the 260 45 acp load from Speer #12

lee 255 rnfp (actual 262 straight ww LLA tumble lubed air cooled sized .452
cci350/winchester large pistol
6.2 unique
1.20 oal ( rim sits and crimps right at the very edge of the bottom of the crimp groove if memory serves me correctly- took a bit of thumb pressure to chambe in the BH cylinder)
taper crimp to .469

Shot very similiar to the 252 swc load, but made a big thwack when it hit the cardboard. Makes a big spray out of a milk carton of water from 25 yards too. Shot well from the Rock Island 45 (until i got worried about beating the little thing)
extrapolated from speer #12 260 grain 45 acp load. Again, no chrono so i have no idea how fast they were moving. But a 255-260 flat at 650 served the british emprire for 80 years!
I liked the heavy acp loads in the ruger, basicly because they used less powder than my ruger 45 colt loads ( 10 unique under both bullets) I never shot anything but paper and water jugs with them. Recoil was light. I would work up to these, as they are pretty close to the top of the speer chart for this weight in 45 acp. I quit loading them because I kept being tempted to shoot them in the 1911. If I don't make them, I won"t shoot them. Though either one would make a good SD feild carry load for a 45 acp cylinder in the blackhawk.
Jason