Andrew,
The point of self-defense firearms is to neutralize a threat to you. If this happens to cause a fatality, that is one outcome, not neccearily the only outcome and not neccessarily the best outcome.
Listen to the others that talk about not going where there is a potential threat, find a different camping spot. Should not be too hard.
Now on to self defense firearms. If you are interested in the 12 gauge, that is a good choice, although it is a 2 hand firearm. Make the first round a load of "rubber" shot. The police use this during periods of riots where they want to repel, not kill. And it is very effective. A subject fired upon with this stuff will have the wind knocked out of him, and while he is turning blue, you will have a chance to run. Load the remaining with something like 3 inch number 4, good pattern density load.
As for California, I can not reccomend you carry a handgun, because of what I have heard about the political climate. But any good caliber that you are familiar with will do, self-defense gurus tend to stay away from the hard kicking rounds like 41 mag, on up, the rationale being a quicker followup shot, and no collateral damage from overpenetration. If you pinned me down, I would go with 44 special. I don't like autos. Or a revolver in 45 acp shooting moon clips.
Any good rifle from 22 on up will suffice.
Like I said before, Please listen to the others, do not put yourself in a situation where you will need to take a defensive stand, and make sure you exhaust all your other options to ending the conflict before you fire.
Be Smart.
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Safety,Ethics, Accuracy, Velocity, Energy-I am On the Way to the Arizona Predator Hunt!!!!!!