Are you asking what caliber is cabable of taking down a Grizzly bear? Pretty much any calibur will kill most animals if you shoot it in the right place. Infact, one of the largest bears ever killed in North America was killed with a 22. Shot right behind the ear. Ofcourse nobody in their right mind would rely on a 22 for protection agianst bears. I'm just saying..
If your asking what I would take out with me into bear country for protection? It certainly wouldn't be any small calibur Rifle or any handgun. It would be a large caliber Rifle or shotgun. For a rifle it wouldn't be anything smaller then a 7mm magnum. 45-70 is an excellent choice for bears. I personally would most likely take a 12 guage shotgun loaded with 3 inch magnum slugs. At Close range, this will stop King Kong himself. Buckshot is less effective with Bears. Super Super effective with human beings though. Don't listen to people telling you bullshit about shotguns. Shotguns are some of the most deadly handheld weapons on Earth for most any two legged or 4 legged creatures. You know except for big African game like Elephants and Rhinos. I've heard people actually say they wouldn't take a 12 guage shotgun with them for protection against bears, yet they would take a 44 magnum pistol!!!! lol As if that shotgun is not 10 times more powerful and more deadly. That's peoples retarded logic for you.
Words of Wisdom From Nick Diaz:
ďBack in the day, a Ninja didnít have his girlfriend sitting in the tree waiting to kill shit.Ē