As BB338 said, bowling pin loads are for knocking down those bowling pins (and for tipping steel targets.) Takes a little more ooooomph for those. Usually a bigger bullet and as much powder as you can cram in there.
I'm not familiar enough with the BP cartridge rounds as with the front-stuffers, so I'll just stick with the book info for now.
The .45 Colt cartridge takes anything fron .452 to .454 dia bullets in (relatively) soft lead (#2 alloy.) If you are shooting harder lead (wheel weight or Linotype) you should get your forcing cones (cylinder) measured and size at or just a leeeetle larger that that.
Using PdexP, Lyman shows the 250gr (452664) and (454190) at 35gr powder for 910 and 915 fps out of a 7 1/2" Blackhawk. The 255 gr (452424) lists 36gr for 918 fps.
The old rule of thumb used to be, "If you can't get the bullet to seat, you put in too much powder."
This is no longer considered safe practice, even though the metalurgy of the guns is much stronger, these days.
I highly recommend the Lyman BP handbook, if you are interested in shooting dirty. The information on the history and their own test firings is marvelous and worth the price of the book, alone.
Do note that the book loadings show very little spread in charge weights (33 to 38 ...32 to 36.5 ...34 to 37) across eight different powders. This is because black powder and its equivalents NEEDS to be compressed to perform properly. This means a caseful is just about that... a case full. If you want to reduce the load, you need a filler to take up the extra space. Anything from CreamofWheat to Dacron fiber to sized wads can be used. Just remember that the weight of the filler adds to the weight of the bullet: it has to get pushed out the barrel, too.
Hope this helps. Ask some more, this is fun!