They've been killed with arrows.
They've been killed with muzzle loaders shooting 225 grain roundballs.
However, the people using those weapons had a larger incidence of the bear coming back to bite 'em. It didn't happen all the time, but fairly frequently.
I recall reading that the standard advice for the early beaver trappers, who were armed with flintlocks, was to wait until you could stick the muzzle in their mouths. Then light 'er off. That was the best way of assuring a central nervous system hit under dire circumstances.
Of course, I think much of the problem back then was, the charging grizzly already had the ball in it's chest and the trapper was unloaded. I guess they almost never passed up a shot on a grizzly.
The trappers also developed a reputation for partying and drinking like it was their last day on earth.
So, go ahead, hunt griz with a .44. And when you're in town, drink like there's no tomorrow, for indeed there may not be.