10mm will have to be hand loaded to exceed .357 mag, most factory ammo is somewhat downsized, and when yo play with crazy ass reloads you need to test pistol function, change springs, etc.
Ive seen when the smith and wesson 10mm/40 smith revovler has been loaded to rediculous levels and exceeds most .357s.
So 10 mil will be near a .357 and has good penetration for bear defense, but theres a lot of factors to look into.
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