sal,
I cast and shoot that bullet, the Lee 452-255- RF, it drops about 265-270 grains @ 0.452-0.453" with "my approx" Lyman #2 wheel weight alloy mix. I also water quench, then run through my 4500 lube sizer witha 0.452 die with lyman beeswax alox stick lube.
Have also cast and shot as dropped with Lee tumble lube.
It shoots well out of my 4 5/8" New Model Ruger Blackhawk, gives hand size grouping a 25 yds with iron sights, and I have shot it from velocities in the 750 fps (with Trailboss) to over 900 fps with heavy loads of H110.
You ought to tryTrail Boss, I had standard deviation numbers in velocity, in the single digits, shot over my Beta Chrony , with verry good accuracy.
I'm looking forward to buying a Rossi .45 Colt lever gun and plan to shoot the 452-255 in that also.