Use your head is the best advice.A bear charged up by hounds is big adrenalin for the bear but how you control yours means alot.I have witnessed great shooters fall to pieces when the chips are down.Now I know of no way to try to practice this,but I run to get my blood pumping then shoot with what I plan to use.I have seen 44mags take lots of bear with 300gr xtps,wfns,and cast core factory loads,and 45 colt hard casts from 260-300s.I have seen tried some smaller calibers with not so great results,so from my experience a 44 would be minimun.I have seen a 500 S&W used and they work,but aren't necessary.Learning to shoot under pressure is the key,any way you can prepare for that is good.

"If you get to thinkin' you're a person of some influence,try orderin' someone else's dog around" unknown cowboy