If I may insert some facts here: There is absolutely no reason to carry a firearm for self-defense against mountain lion attack, because it's not going to happen to you. In the last 23 years, nine people have been killed by mountain lions in the U.S. and Canada. Want a statistical comparison? An average of 13 people are killed every year by falling vending machines. Do you worry about being killed by a vending machine? You are hundreds of times more likely to hit a deer and be killed on your way driving to your hiking trail than to be killed by a mountain lion on the trail. Even non-fatal attacks by cougars are vanishingly rare.
The fatal attacks that have occurred fall overwhelmingly into two types. The first type is on people - especially women, who are smaller and closer in size to a lion's natural prey - who are jogging or bicycling in mountain lion habitat. Thus they are also moving like prey, and trigger a chase response. The second type is on children - again, prey sized - who become separated from adults in lion habitat. Usually it is young lions in edge habitat who are in poor condition that become trouble.
Some people each year are approached by lions who are either curious or hungry, and which are scared off by yelling and arm-waving. Normally these lions will be tracked and shot by wildlife officials, since their potential for future interactions is much higher.
I live in cougar country - they've shown up on the security camera we have in our driveway 100 feet from the house. We don't worry about being attacked. We carry handguns when we hike, but they are for the two-legged sort of predator.