Shot placement, shot placement, shot placement. Failing that caliber. Failing that lots of shots on target. To wit: “The hiker, who has not been identified by Alaska State Troopers, had set out from the Rainbow trail head at Milepost 108 of the highway Sunday morning, said Tom Crockett, a park ranger. He was near the first Turnagain Arm viewpoint, about a half-mile up the trail toward McHugh Creek, when he spotted the bear . . . The man called, “Hey, bear,” hoping not to startle the animal, he said. The bear turned and charged, the hiker later told rangers. The man fired the AK-74 he was carrying . . .
The bear stopped after the first volley of shots, and then charged again. The man fired once more. That time the bear folded into a ball, rolling and running downhill and thudding to a stop in a clump of birch trees about 100 yards from the trail.
newsminer.com reckons the hiker needed 13 shots to take down the 500 – 600 pound bear. Like I said.