This is for Texcaliber, My shotgun instructor, demonstrated several buckshot loads for us, using our shotguns not his. His demonstration was an eye opener. His personal favorite was winchester 00 buck 9 pellet shells, in 2 3/4", and he demonstrated that it was very reliable and repeatable up to 18 yards, in an 18" cylinder bore barrel. Beyond that distance, flyers were to be expected. He explained that if your department issued other brands and that is all you have to work with, no problem unless no shoots were involved, so he taught us to hold off, away from the no shoot, and engage the shoot target ( bad guy ) and expect less pellets to do the job. A Vang barrel might help, but buckshot is not intended to perform well past 20 yards, precision wise. A good patterning shotgun for hunting with birdshot, would put all pellets in a 30" circle at 37 yards with no holes a bird could fly through. I am however very disappointed in your closer test results, I would expect much better, what combination are you using, choke, barrel length, and cartridge combination? I will tell you from experience, #4 buck sucks past 12 yards, not a problem in normal home distances, but not good past that unless you do some homework and try several kinds and different chokes in your gun. What is good, for defence? An 8" pattern at the maximum distance it will deliver it. Let your pattern be your guide.
GOOD LUCK