I agree with you. I have an M&P340 and it's great for what it is but I can't imagine shooting bear loads out of it.
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I get it that the OP is talking Black Bear , not Grizzly. They're smaller, unlikely to go out of their way to maliciously attack you just for fun , etc .
And in such context I'm not going to be absolutist with " start with 300gr .44 mag and up " . But more than a lightweight J Frame is called for . Even if .357 mag is your caliber choice , a bigger gun . Think medium frame 4 inch . Think belt gun, not pocket gun .
In-between options include .45 Colt , .45acp , ( non small snubbie) .44 Spl . 10mm ( with mainstream loads , not necessarily Boutique hunting or Nuclear Handloads .
Short bbl Vaquero , 4.25 in .45acp , G29 , 4 in .357 , etc can be casually concealed under your flannel shirt , hiking/ fishing vest , etc if that's a concern , deep cover pocket guns not required in the woods .
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Even in areas where Black Bears are common , human threats are more likely. My cliché is that I could deal with pot growers and meth cookers better with a .44 or. 45 , than dealing with Yogi with a .38 or 9mm .