The problem with .45 Colt loads is that they're made for the lowest common denominator, which is the guy with the 19th century Colt SAA who pulls it out and wants to fire off a few. It's been a while, but I seem to think that you can expect about 800 fps out of a 220gr lead bullet. Not stunningly powerful by any stretch. I think they're about the same as your typical .45 ACP round.
You can load them up a lot stronger, but if you're going to handload, might as well do the .454 cases and get the bullet that much closer to the forcing cone? My SWAG is that it would be more accurate with the bullet as close to the cone as possible. I remember my uncle telling me not to shoot .38 specials in my .357, but I can't remember the reason, so I'm guessing a bit there...