Bear spray is supposed to work quite well...I have no experience with it but do have experience with the equivalent on people (retired law enforcement) and it worked. If you carry a handgun, first make sure its legal to do so. Then, pick one that is reasonably light and easy to carry holstered, because you will carry it up and down mountains a lot and probably never have to use it. The ideal would be to carry both spray and a handgun. Killing a bear is a last resort and could put you in legal jeopardy if the situation is at all unclear to the investigating officers.
If you ever do need to use a handgun, penetration is what is needed. It is also a good thing if the handgun can be drawn and fired rapidly. My choice would be a 4" barreled double action revolver in .357, .41, .44 or .45 caliber. The .475's, .460's and .500's are very heavy and kick too much for rapid fire. Single actions are slow and awkward for most people to use in an emergency.
In .357, I would use a 160 to 180 gr. WFN hard cast bullet. In a .44 or .45 it would be the same type in 250 to 300 gr. weight. I would want a velocity of at least 1200 fps. Penetration would be adequate with any of them. If you place the bullet properly, they work; if you don't, they don't.
Yup, I agree for the most part except.....caliber - stick with the .44 mag and hard cast, deep penetrating (Keith-style) bullets. Not too much recoil especially with .44 special practice rounds. Carry full power loads in the field and practice with them a few times. Three important things to do after you get the weapon. 1) Practice; 2) practice; 3) practice.
I witnessed a California Highway Patrol officer shoot a vehicle-struck mountain lion three times with a .357 using 158 grain flat point jacketed bullets. The lion ran off. The officer is a Hunter Education Instructor and a Rangemaster for the CHP. I trailed the lion for 400 yards. It was holed-up in some cat claw brush. Down but definitely not out, a 12 gauge slug ended that little fracas. I covered three .357 entry wounds with one hand. All three were roughly centered on the left shoulder. Nicely placed shots but.....
My bear experience is limited to black bears. They are tough customers. Some will retreat when fogged with pepper spray, others just get really "upset". First, it takes a long powerful jet of spray for it to work and those larger cans of spray are not made for packin' around in the woods by a hunter. I've seen backpackers carrying them but they don't like those big canisters taking up room and weight. Those small cans police carry or the purse-sized cans for women aren't for bear-sized animals.
Second, be mindful of the wind when using the spray. If you let loose with a jet of spray and the wind is in your face, that's all you've done is given the bear a little extra flavoring for his meal as the spray blankets/blinds you just prior to the bear's attack. Also understand that humidity (heavy dew, rain, fog, snow, etc.) will influence the spray's effectiveness.
IMHO, I would carry a 4" .44 magnum with heavy cast bullets and at least one speed loader loaded with same. On a charging bear your point-of-aim will be the bear's nose (an easy reference point causing a person to aim at a specific point - "aim small, miss small"). Hit high and it's a brain shot. Hit low and the top of the heart and at least one lung will be hit. Skip the bear spray. You carry the most powerful weapon ever known to man everywhere you go. Your brain. Be aware of your surroundings, look at ( and
see) what's in front as well as behind you. Listen for "out-of-place" sounds (cubs playing in the leaves, "woof" as momma warns the cubs of approaching danger, the sound of "popping" jaws indicates a "nervous" bear, etc.). Boars sometimes reek, you can smell them from down wind. Tracks will let you know that bears have been in the area.
I've retired after thirty plus years as a game warden. Nature is a tough task master. Unlike our places of higher learning, Nature gives the test first, then teaches the lesson. If you live through the test, you've learned the lesson.