Ive used a good bunch of IMR 4227 in reduced loads for cast bullets in a number of rifle calibers.
In my experience you can try to go too slow, which results in more residue (it is not 'unburned powder', just look at it under a magnifier and you will see that, but it is dirty), or you can use too light a bullet which probably reduces the back pressure needed for it to work best.
Even so, at about 18.0gr. in my 30-40Krag, 30-06, and 38-55 it works great and the velocities are not over 1450fps. I can load heavier and they would still work to the point of leading, but the burn would just keep getting better. Over 1450 I would switch to jacketed anyway, but I like cast bullets. It may not work as well in smaller calibers, ie, the .25s and .224s because the heavy bullets for those may not be heavy enough, though Im not sure. I use H335 in my 25-35.
I think I recall info about 4227 in 45Colt, never tried it as I like Unique and have recently been working with Trail Boss with satisfaction.