It would depend on the weight of the gun and how hard and accurately he could throw it
Honestly, I would not be the slightest bit apprehensive about hunting your typical 350lb black bear in my neck of the woods with a Ruger 10-22 and quality ammo like CCI mini mags. I've seen enough large animals killed with a 22 to know better. A 22LR from a rifle will absolutely pierce the skull of a charging black bear as well as reach It's vitals with a broadside hunting shot. If you dump 10 Rounds into the side of an Elk, wild hog, black bear, etc........ they will go on to death run and collapse just the same as if you put a round of 00 buck into them. I grew up in a very rural area were poaching was quite common. Unfortunately it was something that I was subjected to quite often as a kid.
Brown bears are a whole nother deal because a 22 won't reach their vitals without perfect shot placement. Their skulls are too thick, and they're just simply too big of an animal to cause significant damage with a tiny bullet like that without some luck being involved. With that being said, brown bears are commonly baited and poached in Alaska with 22s from a stand.
