Don’t need a S&W 500 or a shotgun, a 44 Mag snubby will do. When the bear is about 7 yards out, put a 240 gr hard cast flat point thru its nose, (the nose is a lot bigger than its eyes) and quickly step to the side. (À la matador) If the shot is slightly off, I do not fret, for the bear is nonetheless temporarily stunned by the blast, the fireball, and the bullet, so it’s a simple matter of emptying the gun (and busting up) its shoulders. Done like dinner.
Accurate shooting skills mandatory, and … tener cojones.