Ive seen several people shot with 12 gauge buckshot. And from a pure damage on target angle, the 12 gauge is probably king for shoulder fired weapons.

That being said, I think many times the difference is more academical than real world. For example. Lets take a single round of 77 grain TMK center chest. The round is immediately going to fragment the entire front end and absolutely shred the heart. Is a round of 12 gauge 00 buckshot center chest going to do more damage to the heart? Yes. But either way the heart is going to cease function immediately. In my experience good hits with either are usually fight stoppers.

The only places where I think the buckshot has a legit advantage are sub optimal hits at slightly longer ranges where the buckshot spread has better chances of hitting vitals. Also maybe with head shots. We've had several cases where a 223 round has hit the thick bones of the face or teeth and diverted at an extreme angle and come out the side of the face. I find it highly unlikely that all pellets from buckshot would do that. I havent heard of that happening.