About 8 years ago some guys fishing in Alaska were attacked by a Brown bear.
One by the river had a Mossie 12 'cruiser'. He saw the bear running down the hill, racked the slide of the 12 and then couldn't remember if he short stroked or not so he dropped the gun in the water and dove into it!
Two of them on the hillside, with 9mm pistols, opened fire on the bear as it passed, breaking the hip bone, and the bear tumbled down the bank and died.
Well the guy in the water came out. Found his 12 gauge and check. Gun fully loaded so he didn't short stroke it.
But notice the 9mms broke the hip bone.
All is well that ends well!
And another one used a 9mm.
Both accounts are here.
BTW, Grizzlies have been killed by hikers with .45 Autos when attacked.
But he emptied the mag and the bear WALKED OFF and died.
And here is one with a .454 Casual (but he said it was luck shots.)
And another .454.