This thread is found in every gun forum, some say is shotgun's, some the magnum rifle and everyone's favorite the handgun, this is repeated over and over.
All I can say is The best tool ever devised to deal with bears is between your ears.
Study on bears, understand them as much as you can, what attracts them and what sets them off.
If your plan is hopeing for a brain shot, get it right the first time, think big, hairy pissed off terminator tearing you up with teeth and claws while throwing you round like a ragdoll.
The eyes are boney loops on the sides the skull, and the nasal cavity is not a direct avenue to the brain as most would suppose, you get a chance look one over I'd suggest you do.
I'd studied a tagged brown bear skull for hours thinking the very same thing you fellas think (good ole brain shot), in the end its best to avoid them as much as you can by how you conduct yourself, even if you'd of fatally shot a attacking bear theirs no guarentee that it wont kill you before it expires
If the Brain was a primary effective target to immobilizea agressive bear it'd be taught relentlessly to all people that work afield in Bear Country, But they dont and for good reason (very hard to hit).
At best agencies and outdoor professionals primary ploy is to train to get bears to lose interest (bear spray) or as last resort to curtail a attack by wounding the bear with a large heavy projectile that is capable of making its way through thick hide, muscle, sinue, bone, to hurt the bear and get it to disengage its attack.
Any place you walk, City&Town or Rivers & Mountains, you pay attention to where you are and your surroundings, allert to threats, wither the seedy end of town on Saturday night or a willow lined river bank, (You get my drift?) are just as hazardus.
Pound for pound, push for bite the bear wins every time, You choose to ignore the warning signs nature provides at your own risk.
Hunting Bear a .243winchester or a .38 will do (documentd cases of this).
A enraged or agressive bear pumping with adrinalin coursing through its veins is a whole diffrent story!
(documented case of young griz attack on YK delta hit by sabot slugs a total of 9 times out of 14 rounds fired in the 25 second attack only 2 were in a vitals area the rest sprued off bone and musle).
A firearm as defence from Grizz attack? If your carelessness has gotten you to that point their's only one option, allot of Hurt in one shot and thats 12ga Slugs, anything else is forplay before the Human Buffet opens for business.
Like they say there is no Crying in Baseball and No brain shots on bears.
Bear Guns are like Four Wheel Drive.
A little common sense goes a Loooong way in avoiding a sticky situation!