I am not a gun writer. However, that won't stop me from expressing my opinion.
To me, stopping means; "to stop momentum in my direction - now". That can mean shooting a charging bear, buffalo, etc. to break the shoulder and now their path is turned, or stopped - allowing me to put another shot into them, perhaps more precisely aimed (this one to kill them). In my mind, stopping a charge like that will be easier with a large caliber, heavy bullet than it would be with a 100 to 140 grain bullet - even if placed in the boiler room. To clarify, to me stopping calibers begin at .338 (250 grains) and go up from there.
Of course a shot to the brain or CNS would be better than one to the shoulder, and would certainly stop a charge. However that may be more difficult to hit in the heat of the moment (the head bobbing up and down) than the shoulder. But I am not speaking from personal experience.
I recall many accounts in various books where the author tells of a charge where the animal was turned / stopped and then finished off (if that first shot didn't also kill the animal). That is the scenario I envision.
I have only been charged once in my hunting life, and that was by a very confused / frightened squirrel. You will be happy to learn that I was unharmed by the crazed beast. I fired at it in self defense, as it ran straight at me, and it met the full force of a load of #4 shot / 12 gauge at approximately 10 or 12 feet. I was about 14 or 15 yrs old at the time.
