10mm is adequate if loaded with the correct ammo, i.e. a 200-220 gr cast lead bullet at 1200fps or a heavy copper solid at high velocity. I believe it was in the 2019 moose hunting season on Elmendorf AFB in Anchorage, AK that an airman went looking for a downed moose in a alder patch, got charged by a brown bear (the grizzly’s larger Alaska cousin), and Glocked it with two shots to the head using the aforementioned heavy lead bullets. I’d still rather have my .45/70 though...
yessir, that’s right... 220gr cast lead FP is the go to. I hear ya on the .45/70... better terminal performance on bear.. in my training, we put lots of rounds (4+) on target to blow out spines (hips work too) and create unpluggable holes. Now the unpluggable hole scenario is for a different purpose than the subject matter of our discussion. My carry sidearm is a Glock 19, so I like to roll with with the Glock 10mm in bear country only because I have so much trigger time with the Glock platform... and 15+1 10mm with rapid mag change capability feels good. Yes, I know... the bear is done of you’re done before you run through the mag, but still. lol.