I did some testing with Buckshot some years back.
Gun was a Benelli SBE 3.5" 12ga.
Choke was a Pattern Master custom tube, this tube is made with buckshot & large steel shot in mind (BBB & T steel). It did about the tightest patters of buckshot I've ever seen on paper. But a paper test does not show you how well it will penetrate. SO..............
2nd test!
Target was a 1 gal. milk jugs filled with water. Load was Fed. Premiums 18 pellets 00 buckshot.
1st. shot = 30yds with 11 hits on jug which all exited.
2nd. shot = 40yds with 6 hits on jug & all exited.
3rd shot = 45yds with 5 hits of which 4/5 exited.
Based on failure of 1 pellet to exit a plastic milk jug of water I figured that was about it for buckshot for MY gun & choke combo as water does not give as much resistance as muscle & bone.
I would like to say however that I have to agree that everyone who intends to use buckshot MUST pattern test & determine how far it is going to be effective through that gun & with that load. A change of load should mean more testing & of course the same for any change in choke used.