Sniper2,
I would not hunt deer with a .17 rimfire even tho a .17 would no doubt kill a deer. That is how I feel about hunting brown bear with .30 cal. rifles. When you see one coming hard they are NOT from this world - I doubt that you could have too much gun. I came away from Alaska with an entirely different outlook towards bears. I have a lot of experience with black bears, a bit of time with grizzlies - had never seen a brownie. Brown bears are evil, they are pre-historic killing machines, they are not nice looking, they have beadie little eyes, very small brains, enormous muscles on their jaws that are made for one thing - killing, their shoulder muscles are about the size of your waist (unless you are a chubby guy like me). Any bear can scare the crap out of a person when they get aggressive - bown bears are worse. They can be very vocal, which is an intimidation thing that works. They are not that nice of an animal, despite what that guy from California that got munched was trying to tell the world.
Personally, I would not hunt one intentionally with a .30 or .338 mag. - simple as that. Hope to do it again, it will be with a .416 or bigger.
One brown bear kill does not make me an expert by any means, but I got some strong opinions on them big furry guys.