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...