I've only shot 2 black bears with my 20 bore. One was 24 feet away , [ the length of my shop at the time ] and the soft lead ball over 110 gr of FFg went through both lungs and exited , the bear spinning around and spraying the wall , then dropping. He was a 2 year old male who was very very hungry, and had tried to eat my dog. He woofed at me, shook his head, and was extremely aggressive when I interrupted his attempt at a meal. I was alerted by my dog's howl of terror. Luckily, paper cartridges load quickly.
The other bear was shot at about 30 yards, and the round ball went through both lungs and nicked the top of the heart, but did not exit. The bear went about 20 yards and dropped. I have cast some WW .600 balls, but haven't hunted with them as yet, preferring the 10 bore for most of this kind of work. I've no doubt that a WW ball in the 20 would pass through a bear, and do a good job but since I have the 10.....
For interest's sake, I have used foster type slugs in my 12 g pump in the past, and had them break apart on heavy bone . I took some shells apart and switched the slugs for .690 WW balls with excellent results. I really believe that a large round ball ,soft or hardened, depending on the game, is about the best hunting projectile there is within practical range limits.