my 2 cents, you cannot just claim any caliber, and think you will have like success, every case has different variables
from what BULLET was used, which is a HUGE deal when dealing with dangerous game
what condition the animal was in when shot
considering most all bear charges are BLUFF"S, if were being honest here
how many ATTACKS were bluffs and or full on attacks , and WHY were they being attacked, were animals injured, were cubs involved, was bear starving or other wise injured before this attack, or were injuries caused , causing the attack
what SIZE was the bear
there are just so many differences here, no one can say "X" caliber will work 100% of the time!

then add in what experience the shooter has, HOW was the shooter before attack, was gun in hand, was gun in a holster, and so on!

Bears have been killed with 22 caliber guns, some times LUCK plays a BIG role in the outcome more than caliber and experience does, again IF were being honest!

typically the name of the game in dealing with any dangerous game animal, is , simple
you use the biggest caliber , with the best FOR ANIMAL bullet, that you can shoot well and handle recoil well

after that, when in an attack, it sort of comes down to LUCK IMO
adrenaline does a LOT of weird things to humans, including ruining how well we shoot!

as also, keep in mind folks, a bear attack is a super, super rare thing to have happen, even in heavy populated high density bear places!
heck in places like AK and BC< as a FACT, your more likely to get attacked by a Moose than a bear by a LARGE percentage!

and keep in mind, we are human and as such, that means, we can make mistakes and not be ready if when an attack comes, , BLAH BLAH BLAH!
I have read many books on bear attacks as well as talked personally to a few folks that have been in attacks and lived! they all told me LUCK mattered more than there shooting skills did!

and for decades I have been about guns and big game being shot with calibers from tiny .22's to Big 50 bmg and some larger bore calibers! in more than a hobby way!

have seen "X" animal , be it a bear, deer , elk, ???
shot with them BIG guns and run and live a long time, and have seen same animals shot with 22's drop in there tracks
Bullet placement and what it hits matters period, and why archery gear works!

my rule of thumb in big bear country is again using the larger caliber I can handle well, and shoot both with strong and WEAK hand, and its loaded with bullets made for the task!
'd also carry bear spray too!

been in AK and other places with big bears, have been up close and personal with so many bears folks wouldn;t believe me, or all the things I have done with them!(i have crawled into ear dens with sow's and there cubs!)

and to date, NEVER had a single issue with one, using bear SMARTS in BEAR area's , IMO< is one of the best things to learn before you go, into them places
as they knowledge is power,
bears are not out to eat you 99.9 % of the time, to be honest to bears we humans STINK< and they do there best to avoid us
far too many people fear what they don't know , which can lead to BAD results IMO!
I don;r fear bear's, even the BIG one's
I do however RESPECT them!
for what they are
but I spent time learning about them to know what I know! and recommend anyone venturing into BIG bear country to spend there share of time learning about them, over just relying on shooting skills and "X caliber hand guns
lots of ways to AVOID a bear attack, over worrying about being in one IMO!