On the Accurate reloading forum a report of a Polar Bear being killed with two shots by a .222 at 80yds.
Not much room for error - but put any bullet in the right place results will be certain.
I suppose if you think about it a 222 has energy of c1000 ft/lbs, whereas a 375 H&H is around 4000 ft /lbs - 222 plenty for fox, small roe etc weighing 10 to 20 kgs. 375 H&H considered plenty for Buffalo weighing 1000 kgs - that is 50 to 100 times bigger with only 4 times more energy. Even if you go to 460 Weatherby Magnum at 7000 ft/lbs it is only 7 times more energy!