MG, You are a lucky man to have a shotgun that will shoot so well. When I did my buckshot testing, I used three 12 gauge shotguns, with multiple chokes, if available, one sixteen, and one 20 gauge gun. I shot numbers 4, 3, 2, 1, 00, and 000. I never did find a combination that suited me. That said, I did kill a doe with the 16 gauge, an old Crescent s/s that belonged to my wife's grandfather and which he had sawed off to use for rabbit hunting. I shot twice at a doe at 25 yards, and I found that 2 pellets had struck her, both in the lungs. My impression was that I had totally missed with the first shot, and connected with the second. She ran about 80 yards across a large open field before she collapsed. Had she run back into my land, she would have been nearly impossible to find, as there was no blood trail.
I only tried buckshot because the next county over is shotgun only and there are some really thick areas where I hunt. Generally, I use slugs and have not lost a deer to a slug. In Virginia, we have some counties where buckshot is the only option. They are mostly in the eastern part of the state.