I have been on this website almost since it's inception. I have recieved an invaluable education in backcountry hunting from the impressive collective knowledge of the members of this board. I have followed the bear defense discussion first with ammusment and now with consternation. Consequently, I now feel compelled to offer my opinion on what I have observed concerning the bear defense topic.
Let me begin by relating my experience in this area. Please understand that this is not presented in a boastful manner or as bluster. Rather, it is presented so that the reader might judge the validity of my statements. I spend 7 days a month June, July and August fishing in Alaska and have for a number of years (brown bears). I fish Hudson Bay for brook trout (polar bears), hunted the Brooks Range (grizzly) and canoed the Boundry Waters (human habituated black bear) and bear hunted on Admirilty, Kuiu, north of Cordova and the Kenai Peninsula. I have been trained in the modern technique of the pistol at Gunsite. I have never shot a bear in defense of life or property but I have killed them. I have been"charged" more than once.
The posters I have seen on this subject include combat pistol instructors, military personal, hunters and fisherman. While all these gentleman are experts in their fields, the first question I would ask anyone offering bear defense advice is: How many bears have you dissassembled? I measured the 2 black bear skulls and 1 brown bear skull I have in my posession. The brain cavities of the black bear skulls are 3" wide by 5" long. The brown bear brain cavity is slightly larger, 3.25" by 5.25".
My thoughts on the subject of bear defense. Bear attacks are not firefights, magazine capacity is irrelevent. The difference between a bluff charge and a real charge is the last 10 feet. Go read the Alaska Game Regulations. You better know the difference between bluffing and real because the Sourdoughs take a dim view of Pilgrims unneccessarily ventilating their bears outside of hunting season and especially without a non-resident bear tag (big bucks) and a guide (bigger bucks). Bears are fast. Their heads are not only coming at you quickly but they move side to side. Bears have big bones and bigger muscles, thats why penetration is paramount and hollow points are a mistake. Bears are hard to kill when adrenalized but die fairly easy if you shoot them in the right place before they get pissed. However, if you shoot a bear that won't get you shackled when the fish cop comes to investigate, he's gonna be pissed off. Bears are scary when they are mad. They pop their teeth and drool comes out of their mouth. That is why I would trade the weight of a double stack magazine for a clean pair of skivvy shorts. If it is a bluff charge you are going to need to change the ones you are wearing. If it is a real charge and you shoot him before he gets to you, a costume change is still in your future. If the bear gets to you, you can use the clean shorts to tie your scalp back on and your dirty shorts are the least of you worries. I believe that is what Patrick refers to as dual use.
Semi auto rounds, with the exception of the 460 Rowland, are only useful for shooting a bear in the brain because they do not have the penetration or the permanent wound cavity to be effective otherwise. It is a mistake to trade penetration for wound cavity by using hollow points. If you crank up the 45 Super to where it equals the 460 Rowland but don't put a compensator on the pistol you will crack the frame. When? Who knows but if you practice like you should, it might be when you need your sidearm the most. The 10 mm is not the equivilent of the 41 magnum. I've got the chrono data to prove it. If a revolver in an effective cartridge is too heavy, carry bear spray instead.
Some general firearm observations. Pay attention to revolver cylinder length. A longer cylinder allows a longer bullet which equates to better sectional density resulting in greater penetration. You can also seat the bullet out to the next driving band and get a little more velocity at equal pressure by using a little more powder. Single action revolvers handle heavy recoil better than double action revolvers. Double action revolvers come back with a straighter impulse and even rubber grips do not completely attenuate this characterisic but make sure you use a grip that covers the backstrap. In adequate cartridges with heavy for the caliber bullets, you can cock a single action as quickly as you can return a double action to battery and pull the trigger. Splits on a timer prove this. Reloading is not much of an issue because other than a 41 or a 44 nobody makes a speedloader. You are probably only going to get 2 rounds off. If 5 or six rounds has not done the trick and the bear is chomping on you, I don't see a speed reload in your future, regardless of the type of sidearm you are carrying. If you are not the one being eaten, after 5 or six rounds you have probably ventilated your buddy some and he can ponder whether you or the bear has caused more damage while you reload. Never heard of a multiple bear attack so an "Attack of the Zombies" scenario is probably not realistic.
Specific recommendations. Minimum in black bear country 357 magnum with 180 graind flat nose. Minimum in brown bear country 460 Rowland with the heaviest bullet or 44 magnum with 300 grain wfn. I believe the 41 magnum tauraus ti tracker with 250 grain wfn is equal to the 44 mag with 240 grain Keith. I carry a 475 Linebaugh with 425 lfn in brown bear country. If you can't afford a Freedoom Arms, the Magnum Research BFR is just as good except it is a little heavier and slightly more bulky but it has a longer cylinder. I use an El Paso Saddlery 1942 Tanker holster because it is compatable with backpacks and flyrods. Best book "Bear Encounter Survival Guide" by James Gary Shelton. ISBN 0-9698099-0-5
Disclaimers. Your mileage may vary. Patrick disagrees with me about semiautos. Phil Shoemaker disagrees with me and he has taken apart way more bears than I have (see his article about pistols and bears he wrote for Wolfe). My parents never worked for the RCMP. I have never cruised timber nor have I ever fought a forest fire. I only cut down trees for firewood, not for a living. I have never been in a firefight.