I wonder what bullets he was using in the 10mm. When I lived in Colorado my house was in the mountains NW of Golden and right next to the Roosevelt National Forest. I usually had one or more black bear encounters every year of the 22 years I lived there. I spent much time outside cutting and splitting firewood during the summer. I looked for several years trying to find an acceptable bear defense gun for doing outside work where almost all of my neighbors were liberals who had moved out of Boulder and external carry of my 44 mag would be a problem. I finally settled on a Kahr MK40 stainless 40 cal that was small enough to fit in my front pocket in a pocket holster. For ammo I used Double Tap 200gr Wide Flat-Nose Hard Cast lead bullets that tested at 1000 fps in my barrel length. Recoil was not intolerable and the bullets should have had plenty of penetration and bone busting capability. I am pretty sure that same bullet was available in 10mm loadings and would make a great bear defense load. At the time this bullet may have been available in .357 mag, but 40 cal was the smallest caliber for semi auto and why I picked it. The Glock 29 10mm would not fit in my pocket.
Today the Underwood Defender solid copper bullet would be my choice and are available in 9mm which would give more rounds in a pocket carry size.
“..and external carry of my 44 mag would be a problem..”
It would be neighbors problem..not mine!😎