I carry a .22 autoloader with me during deer season. The reason is that California law allows the taking of grouse with a .22 pistol. It is far easier to manage then having my shotgun slung over my back while carrying a rifle.
Admittedly in a couple of areas known for "Dinner Bell" bears I carry a .357 while deer hunting. If I go looking for a couple of grouse for camp I will take the shotgun and a few rifle slugs incase a need comes up. I realize that if there is a surprise encounter there may not be time to change rounds but up close #5's in the face can be rather nasty.
My game plan has been to take on bear with my deer rifle. But that plan may fail. On a back pack hunt I killed a deer on a steep hillside. I laid my rifle down along with my pack, and gutted the deer. I then started carrying part of the deer down to better location. A rattlesnake sounded off near my feet and I kicked into overdrive. The problem was that the snake was between me and my gear. And the snake was hid in the grass on the easy way up the hill. I worked my way back up the hill to my rifle. I then located the snake by tossing a couple of rocks in the area I thought the snake was. The snake sounded off and I was able find him in my cross hairs. I can testify that the .270 Winchester is a very effective snake gun. The bullet cut the coiled snake into three chunks.
If it had been an aggressive bear I would have been in trouble. Just me and my skinning knife. I do not like those odds. At that point a .22 pistol would have been welcome. Not great but better then a knife.
The point is a hunters rifle may not be handy in some situations. When we camp in some bear prone areas you might see us wearing hand guns in camp. The rifle is not very handy when you are cooking or doing other camp chores. Most of our bear problems went away when the bear season and deer season opened on the same day. I believe black bears are more agressive in areas that they are not hunted in. A classic example is Lake Tahoe. Both on the California and Nevada sides. They have nothing to fear.
If you happen to find me in a tree you know I am in trouble.