About 30 years ago, the Police Marksman's Association tested buckshot and chokes.
They used an 870 with riot gun 18" cylinder bore, commercial slug barrel 20" IC, a 20" with Polychoke and a 20" with screw chokes, I think the Walker full thread style.
The very best (tightest) patterns were with Winchester 000, eight pellets in Grex filler, fired from the Improved Modified screw tube.
Things might be different with current shells, but the point was that buckshot responded to choke better than they expected.
Agree with the idea that the idea of buckshot is multiple hits, not scattershot to make up for poor aim.