The
risk the black bears present in California and throughout the Sierra Nevada and Cascade ranges is pretty minimal:
The last fatal bear attack in California was in 2008, but it was a captive bear used in movies that killed a handler.
Before that, an animal trainer was killed by a Himalayan Brown Bear at the San Diego Zoo in 1942.
Those were the only two fatal attacks in California in the last 150 years. Prior to that William Waddell was killed in 1875. He was deer hunting. He was only just bit by a Griz that left him and took off after after his dog (it was the dog that had provoked the bear in the first place). Waddell had his arm amputated by a doctor but died six days later from the infection of the wound, which would have been easily cured with antibiotics developed since. I lived for a little while just down the road from the grave of his amputated limb which was buried near where he was attacked. The rest of his body was buried at the cemetery in Santa Cruz. All the Griz were wiped out of that state by the 1920's.
I've encountered bears in the Sierra frequently, and I never felt threatened.
I'm not suggesting that a person be defenseless, but that these bears are not the threat that you want to arm yourself against. You have a great deal more risk from other humans. Last year there was nearly 5 homicides
per day -- more than bears have killed in California for 170 years. Your risk from other violent crimes is just staggering compared to any kind of bear attack.
Besides that, the Black Bears are not much bigger than people. Most of them are around 200 to 300 pounds. Occasionally an especially big one will top out at 600 pounds. They don't require munitions unique from those used for defense against human attackers they way that brown bear do. Small brown bear males weigh 800 pounds and big ones can weigh 1700 pounds. Those are the bears where ammunition designed to penetrate and expand in humans may not penetrate sufficiently, but they don't have them in California for 100 years now.