‘fraid so. It might work with a 200# brown or black bear. With a grizzly, a can of pepper spray and/or a .45 is more effective.
If you happen to be a liberal, you can always stop a grizzly attack by rubbing them softly between the ears.
Well, that's what I tell my liberal friends, anyway.
You can tell if Grizzlys are in the area because the bear poop smells like pepper spray and will have belt buckles and shoe lace eyes in it.
With a grizzly, a .45 is scarcely sufficient unless the shot is very luckily placed.
There are numerous cases of .357 hits merely angering grizzlies, and a .44 magnum having 3 times the muzzle energy of the .45 ACP is the bare minimum to have in your hand if you want to fend off a grizzly.
“With a grizzly, a can of pepper spray”
...will make the bear think, “Oh WOW! Mexican food!!!” ;)