I don't mean to demean your personal ability, but with a subcompact weapon I doubt you will have enough controlled gunfire to take down a charging bear. Black bears aren't that big compared to many other bears you could encounter, but they can be just as stubborn to kill.
There is no such thing as overkill here, just underkill. Your glock will be underkill. A 12gauge slug will be justenoughkill.