I'm almost embarrassed to reply to this thread, but as a guy who has seen a few grizzlies in the wild (with and without backup), and as someone who has spent a little time flying float planes and tail draggers over grizzly country, I feel compelled to comment.
I always felt best with my old .375H&H or new .416Ruger stuffed in the back when travelling over grizzly homeland. Once I got weathered in on a sandbar with 200+ mama and baby grizz tracks on it. The salmon were running but I didn't fish or eat for the two days I waited for the weather to lift because I didn't want to smell like food. I was happy to curl up with my .375 when I half-slept through the bad weather. When I got home from that trip I bought the .416. Factory loads shoot 400 grains of solid or controlled-expansion projectile at Mach 2. No handgun comes close to that. I've never shot it in anger, and hope I never do.
But the guy is right - you don't always have room for 10lbs or 42" of gun, and survival gear is what you have on your person, not what's buried in the back of an airplane. So you need whatever you can strap to your body and then you hope for the best.
No .44 magnum, .454 Casull, or any other handgun cartridge is going to have the penetration of a .375H&H, or .30-06 or even a .270 or 30-30 carbine, for that matter. That's all there is to it.
All handgun cartridges are marginal for penetration on any bear. A charging bear will give you very little to shoot at. If he bluff-charges and stops 10' away, then still, what do you shoot at - eye? nose? open mouth? Me, I would be shooting at the dirt in front of his snout - after all, it's a *bluff* charge and I'm standing in his living room.
Having seen the video of that McBride (BC) photographer who survived a charge, I'm half-convinced that the "boom" of the revolver does more to stop a charge than any lead or copper projectile running down-range. On that basis, the .357SIG, with its super-sonic crack might be a better choice than a 10mm or .45ACP. And who knows, maybe a fast .357 will penetrate as well as a heavy .44? It's not an exact science, but whichever one gets to the spine will immobilize the bear. If you even have a shot at the spine.
I never had the chance to get a ATT for bush flying (I was based on the left coast and it would have scared off the tourists), but if I had, I like to think I would have put up with the discomfort of a .44 revolver (4.2" Redhawk maybe?) in a shoulder holster, rather than a Glock or similar strapped to my hip. I imagine neither is much fun to wear all day, but any (non-bluff) charge will be over after two or three (at most) aimed rounds, so magazine capacity is not an issue. Thinking about it, a 4.25" .454Casull would be better, but that's a custom rig in Canada, and pilots are notoriously poor.
There isn't a money-earning flying business on this continent with margins so tight that it cannot afford to pack an extra 32 oz if safety is at stake (an ELT weighs several pounds), so we're really talking comfort. Comfort is important if you're flying all day, but between Glock's 27ish oz. empty weight and a short Redhawk's 47oz empty weight (you gotta carry the ammo either way), I doubt I could tell the difference, even after a 14-hour duty day of loading fuel, fish, baggage, and even the occasional wood stove. If 20oz is too much to strap on, maybe you should be at a desk pushing paper (like I do now), rather than flying around small airplanes?
Now that I'm flying a desk instead of a Cessna, I still go to grizzly country on weekends, and I have the same problem: there isn't a proper bear-stopper gun made that's legal for a guy to take fly-fishing in grizzly country. Long guns and fly rods don't mix, and it's not about comfort, you just can't pack a long gun and get off a decent cast.
I've been told that antique revolvers are an option, if you're just packing for the purpose of doing the odd bit of target shooting while off in the woods. But antique revolvers are limited to (at best) the .45ACP, .44 Russian, .44Special and similar. Double-action antiques are rarer still.
No, none of these "little" .44s or .45s will "stop" an actual charging grizzly, but neither will any other handgun cartridge. But they will all go pop, and if, one day, a grizz is stripping the meat off my thigh or clawing at my stomach, I like the idea of reaching into my fishing vest, pulling out a 130-year-old DA revolver, and putting a .45ACP round into his mouth. At that point, the bear might have gotten the better of me, but at least he won't finish the meal...
So dude, buy a polymer-framed .45 if you must, but just be realistic - it'll go boom, and that's all well and good, and it might give you something to do while the bear's dinner is under way, but that's about it. That's enough for me, because it has to be. It would be nice if we had a better carry regime, but this is Canada; we don't. The alternative is not going into the woods, and I can't "bear" that choice...