Get ready to feel the love.
Yes, I'd use my 12ga 870 to defend against any charging bear on planet earth. Above and beyond any rifle from 35yds on in. Some 1 3/8oz Brenneke slugs would be in the magazine.
I'm not hunting bear with my 870. I'm stopping bears at close ranges.
My first round is tungsten buckshot. 9 pellets of #1 buckshot, and 1 pellet of #0000. Tungsten #1 buckshot penetrated 9" of live birch tree trunk in my penetration test. The #0000 tungsten penetrated 14" of live birch trunk. I load these tungsten shells for head shots.
The tungsten buckshot will hit the face of the bear at ~25-30yds, and I'll likely never have to fire the Brenneke slugs. But they would be in my 870 magazine. In case the bear morphed into Tyrannosaurus Rex or Godzilla.
We did finish a wounded grizzly close up in the willows with this combination a few years ago. Deadly...
If I didn't have the tungsten buckshot, I wouldn't feel short changed with solely the Brenneke slugs.
Now, you owe me for the love