If I must carry such a gun, do you know the smallest one that'll do the job? Obviously a 12 ga. street sweeper would be a useful tool in a battle against a bear.
But I really don't feel like lugging around a 12 ga. street sweeper and the 4 lbs of ammo they carry (or whatever it is).

Some say 10 mm is the way to go.
Others like 40 cal.
Pistol, semi-automatic, .45 caliber, M-1911A1... or any variation thereof.  It may only hold 7 rounds, 8 with one in the tube, but every one of them WILL knock a bear down.  And unless it's one that's been machined to "match grade" tolerances, you'd have to work real hard to make one jam.  Trust me.
One source suggested I consider the .357 Sig, not so much for the foot-pounds of energy it delivers to target (there are better carts for that than .357 sig) but because it has fairly good penetrating power (almost as good as a .357 Mag (which you know is a revolver cart.), and it's deemed unusually reliable. I think that means, it jams less than some other carts.
There's only one handgun I know in .357 mag that might jam, and it's because it's a version of the Desert Eagle automatic.  The rest are all revolvers.


image image image
SGT. JIRI TREBISSKY H&D SAS

"When the winds of change blow, some people
build walls and others build windmills."
~ Chinese proverb