After spending a considerable amount of my life in 'bear country' here is my words of wisdom. First there are NO grizzly bears in California. Now a 357 magnum will work on a Black bear BUT shot placement is everything! Better is a 44 mag or if you can handle the recoil a 500 Smith. But recoil recovery takes time and with the 357 you MIGHT be able to shoot multiple times. Bear spray is better because it does not require an exact 'shot' and is usually effective. Bear spray also gets you off the hook legally as you do not have to explain to a ranger why you killed a bear out of season. My advice is carry both bear spray and a gun. Oh and good luck getting a CCW in the Peoples Republik of Kalifornia, if you get a CCW get a lotto ticket too as you would be a very lucky man.