good
To answer your question, you CAN buy High Powered rounds, and you CAN buy low powered rounds loaded for the .45 Colt. Try to find a medium powered round though...
To clarify:
There are a fairly decent number of low powered(Cowboy) loads for the .45 Colt. Most of these are 250gr soft lead bullets at about 800 FPS. Nothing I would volunteer to step in front of, but not my first choice for defence against 2 or 4-legged creatures.
High Power Loads...the two most popular options for non-handloaders seem to be either Cor-Bon or Buffalo Bore. Here is where problems arise: Most(not all) of your Monster .45 Colt loads are listed 'For Ruger or Freedoms Arms Only'. In fact, if you go to
www.Buffalabore.com, you will see they split their .45 Colt loads into Standard Pressure Heavy .45 Colt(Safe for All Modern Guns), and Heavy .45 Colt +P.
For a factory loaded, Safe for all guns .45 Colt load, about the best you can probably do is a 250-260gr bullet at about 1100 FPS(560ish Foot-lbs). This is probably more than enough for defence, since it matches/exceeds most Max loaded 180gr Hard Cast .357 loads, which most folks feel is marginal bear protection. It would be better than a sharp stick anyway.
In contrast, the moster loads move a 300gr hard Cast at 1325fps(1150 Foot-lbs). Serious bear medicine.
Now, trying to find a deer load that doesn't hurt to shoot...that's the challenge I'm facing.
greg