I do not know if you have read this article from the owner at buffalo bore about stopping bear with pistols but its a good read and he should know a thing or two about it, here is the link.
https://www.buffalobore.com/index.php?l=product_list&c=108
Excellent link BigBore45. I've book marked it for the future.
I agree with that article completely, with the exception of the notion that injuring a bear is often enough. It may be enough to drive the animal away, but an injured animal is an animal that will possibly die from starvation or infection. It is also an animal that will be highly defensive if another human runs into it. I believe if you are going to shoot, a warning shot is alright if you have time, as skidder asserted earlier. However, if you are going to shoot to hit, I believe in shooting to kill. JMO
I really do get a little aggravated when I read posts in bear threads suggesting that bears are really no threat to people. I certainly believe most animals want nothing to do with us. But most is not all, and bears are more than capable of killing a human with ease.
To assume bears are not dangerous because you have had run-ins with bears that resulted in the bear retreating is just as silly as assuming that all people are not dangerous because you've never been attacked by a criminal on nut job. It just isn't true.
Your best first line of defense is situational awareness, and noise. If the bear hears you coming, it is more likely to walk away from the noisy human. If it's in a bad mood, I want a big and powerful gun with me incase it decides its in a killing mood. In the case of bears in general, the largest bore with the highest velocity and heaviest bullets you can stand is probably your best bet. Deciding if black bears warrant a big bore or not is up to each of us, and is dependent on what you can stand shooting, and what your tolerance for risk is.