I take it that you’re referring to the 1911?? The answer is YES, the 1911 in 45 ACP is more than adequate for black bear and ole Grizz, as well. Like any other handgun used for “protection” against dangerous game, it’s shot placement with the correct bullet that counts.
If you don’t roll your own, then commercial loads such as Buffalo Bore’s 255 grain cast is what you probably will want to carry.
Stopping a determined charge from any bear is mainly just luck, as most hunters/hikers/whoever are never aware of the charge until that bad boy is within 50/60 feet and has a full head of steam – they cover about 40 feet of ground per second when coming full-on, so most don’t have the reflexes to react quick enough to get their handgun or rifle into action.
You’ll get smacked to the ground with authority and you’ll probably get chewed on a little as well. It seems the vast majority of charges are because you trespassed into the bear’s area and he just isn’t in the mood to relocate that day and proceeds to teach you some manners about trespassing in his domain and he really has no intention of eating/killing you, which is always a good thing – doesn’t mean that you won’t die from the mauling – just that it wasn’t the bear’s initial intent.
On the average day, he will usually just move off and you’ll never know he was around or sometimes he’ll rise up and look you over and just go about his business but if you hit his off-day, you’ll have a real bear story to tell folks.
If you get advanced notice of his intent to charge and you’re able to react properly – you can stop him easily with a CNS strike, but for most of us that would just be a lucky shot. My teaching was to pour the lead to him in the shoulder area, which should either break him down or turn him – either way is a plus for you.
If you’re hunting bear – the 1911 is adequate with that cast bullet. The 1911 has the exact killing/stopping power as a 44 mag, 45 Colt, 454 Casull or the 460 S&W if those other calibers are loaded with 240/270 grain bullets going 1,000fps. The big difference is when the other calibers are using proper heavy bullets at a much higher velocity – they penetrate deeper and that’s normally a good thing when hunting. If shooting from a tree stand – that 45 ACP should make 2 holes using a 255/265 grain cast bullet and properly placed, the bear will probably take off at warp speed and pile up 25 to 70 yards from where shot – about the same as if you used a 45 Colt, a 500 S&W or a 30-06 with 180 grain bullet.