Without throwing more bear defense opinions into the ring, I'll just let you know about my experience with the Buffalo Bore .45 ACP +P loads.
The 255 grain load does not feed well in my S&W 1911 stainless government. The bullet used is a hardcast lead round nose flat point .45 Colt revolver bullet (with a crimp groove), so it is seated very deeply in the case. This makes the COAL shorter than just about any other .45 ACP round, causing the round to "nose dive" and get hung up during feeding from the magazine. Others may have better luck. I'm sure this round works fine in other types of .45 ACP auto loaders, but as with any defensive round, it should be thoroughly tested for reliability in your gun. I chrono'd this round at an average of about 930-950 f/s. A .452" 255-grain bullet moving at 950 f/s has another name - .45 Colt
. But you get this power from a fast-shooting autoloader with more capacity than a revolver. I just wish Buffalo Bore would load this cartridge with a different bullet that wouldn't have to be seated so deep.
The other BB .45 ACP+P round I've tried is the 230-grain FMJ-FP (flat point). BB's claimed velocity with this round is 981 f/s. I have not had a chance to accurately chrono this round, but out of 4 or 5 other BB cartridges I've tested, their advertised velocities are very accurate, maybe even slightly underrated, so I have no reason to doubt that this round is doing something between 975-1,000 f/s from my 1911. This load feeds very well in my 1911, as the COAL is standard. It may not be as hard or as heavy as the 255-grain lead bullet, but it's still better for deep straight line penetration than any round nose or hollowpoint bullet.
If limited to a .45 ACP autoloading pistol for bear defense, these 2 rounds are probably your best option. You could certainly do a lot worse than an autoloader you are very good and fast with, slinging .45 Colt bullets at standard .45 Colt velocities. When people hear ".45 ACP", many of them immediately think of the old standard 230-grain round nose bullet moving at about 850 f/s. These two flat-nosed .45 ACP+P loads from Buffalo Bore change the game, a little.