Ah yes, another bear thread. I know bears are a popular subject because they're the stereotypical "hard target", even though there's other animals (like moose) that are substantially harder to put down.
But to answer your question, 10mm probably would not be sufficient. The most success in that category I have heard is a revolver in .454 Casull. .44 Magnum may work, but .454 Casull is up to 50% more powerful.
Yes, people have stopped bears with less. I have heard of people putting down a bear by unloading on it with .45 ACP. There is also a documented case of a US Marine killing a bear by chucking a log at it. But to reliably stop a charging bear, the round I usually hear about is .454 Casull.
Be prepared to "Get off the X" because it may be running dead and plow right into you, even when mortally wounded. It's a bad situation that you should avoid at all costs, but if you have to shoot, bring enough gun and be ready to MOVE.
