I guess praying for enough penetration to get a spinal column shot, assuming you can even place a bullet with that kind of accuracy at a charging bear, is out of th question?
No one other than Capt. Charlie has commented on my bird shot to the eyes idea. What about super strong mace. It won't stop it if it is already charging but it could make the bear change its mind if it doesn't like spicy food. Besides, some of those sprays have a pretty good reach and disperse in the air. If it can't see or smell, you have a chance to pop off a few rounds.
Lets follow this idea a little further. What about carrying a Surefire flashlight with the extra powerful lamp (120 lumen) on a belt holster (assuming you can do so without playing with it all the times and drainig the battery
). If it is dark, getting nailed square in the eyes will have to blind it temporarily. That may give you a chance to move out of the way of a charge and get a few more rounds in.
I would probably look like Rambo if I ever went camping. I would definately add the mace/pepper spray and a high powered flashlight to the .44 mag (or .500 S&W) and shotgun combo. It's not that much more to carry.