If it's charging you gotta do whatever to survive. Good luck with bird shot, maybe you'll blind it. In a perfect world I'd use #4 buckshot and I'm not talking four ought.

its possible. Blind it, hit a major artery around its clavicle, go through an eye into the brain, or into a fracture line in the skull or its ear. This is with 7 1/2 on down; #10 won't even really break skin unless its 5 feet away due to a heavy pelt. with the old SSG, buckshot or really large pellet sizes, its possible. I wouldn't count on it "bang-flop"ing the bear; Karamojo Bell said it best; "There are a lot of calibers that will kill an elephant, but very few are capable of STOPPING one." If I was hunting/fishing and was in bear country, a few 2 3/4 or 3" slugs would find their way into my upland/fishing vest; dad had a few close encounters with moose during bird season. His cousin killed one at about three feet (charging), due to the sabot breaking through its nose and a few pellets in the eyes and the fact it was a very young bull probably in its first rut. Just because you could, doesn't mean I would.

Regardless of shot size, any shot shell performs about like a slug of the same weight at 10 feet. It is easy to do an experiment. Just shoot a 10 inch tree from that range and see what happens. It sure doesn't look like birdshot when you see a 3/4 inch+ hole going all the way through the tree. My dad's best friend was accidentally killed by a 12 gauge 2 3/4 inch #4 pheasant load under similar conditions. He was a pretty stout guy. The entry wound (about a 1/4 inch above the heart) was a normal 3/4 inch hole, the exit wound was over 3 inches in diameter and took three ribs out with it. That was a terrible accident that happened when I was 10 years old and we have all been extra careful around fire arms since; especially the often perceived as "sissy" shotguns.

dependson the size of the bear where you shoot it why its charging in first place and other things. is it possible? ya anything is possible just not as likely

good luck hitting a charging bear to begin with. they are faster than you think and one shot is all you are gonna get, if that. either way, don't play dead with a black bear. they begin eating you immediately unlike a grizzley or brown that will leave you and come back later.

The twelve gauge at close range with any load is a force to be reckoned with.

The bear would probably stop if hit in both eyes but if it was hit without getting blinded it would just be more pissed off.

At ten feet any size shot from a normal 12 gauge is almost like a slug it should stop the charge.

how hard is it to carry slugs? or a .45? or even pepper spray? but if thats all ya got with is a 12 gauge with bird shot, shoot it as many times as possible!