Here's a quote on the weapons of choice from the Outdoor Life article I mentioned earlier.
How to Outrun a Grizzly...
By Christopher Batin
What to do when you're face-to-face with North America's most dangerous predator.
Weapons of Deterrence
“Encountering a bear without a means of deterring it horrifies people and causes them to run, which is a mistake,” Smith says.
Always carry at least two deterrents in bear country. One should be bear pepper spray, the other a flare pistol, air horn or firearm. Carry one deterrent in your hand; the other should be available immediately, like a handgun in a holster or a shotgun slung over your shoulder.
Bear pepper spray might not be as macho as a firearm, but it provides the confidence to stand your ground and has a proven track record in Alaska. Pepper spray is effective because the sudden, loud hissing sound of the spray and the sight of the billowing cloud of red-orange mist frighten bears.
Smith maintains a database of more than 500 bear-human conflicts in Alaska. Bear pepper spray was used in 65 cases and deterred 61 curious or aggressive bears, for a 94 percent success rate. Of 258 incidents in which firearms were carried or used for bear defense, they were effective in 175 of them, for a 65 percent success rate.
While the .458, .375 and similar big-bore firearms are recommended to slow or stop an attacking bear, a U.S. Forest Service study shows that people have a problem handling the severe recoil of these larger calibers. Smith’s records demonstrate that victims carrying large-caliber firearms often have no time to get off a shot at an attacking bear.
Smith suggests a shotgun and rifled slugs when lethal force is required. “You want stopping power and accuracy. Although buckshot gives you a wider pattern, it divides that energy too much.” Also, unlike some specialized rifle ammunition, shotgun slugs are easily replaceable if you run out of them or your luggage is lost.
“Don’t mix rounds when walking afield,” says Smith. “Always chamber slugs. Only in camp, when you might need to deter a curious bear walking an outside perimeter, should you be loaded with shot. Load one shotshell directly into the chamber. If you suddenly need to use slugs, your remaining shots are lethal loads.”
However, a firearm is no guarantee that you’ll escape an attacking bear unscathed. “Many people carry firearms of insufficient caliber, while others are ambushed so quickly they have no time to fire an accurate shot,” says Smith. “All too often, when attacked suddenly, even the most accurate and experienced shooters miss their mark. While the same elements of fright apply to people carrying pepper spray, the spray’s widespread multiple effect can’t be overlooked."