Just an update for the current ammo situation.
Nine .310" lead round balls - buckshot if you will - fit perfectly in a WAA12 wad. Indeed, in a 3 x 3 stack the pellets are flush with the top of the wad. Depending on the lead alloy these weigh in at .91 ounce to just over .92 ounce.
That said, look up Alliant one ounce 12 gauge load data for Winchester AA or Remington Premier STS and like Remington hulls using AA12 wads. Then substitute 9 of the .31" lead balls for shot and finish loading as normal.
These are not long range hunting buckshot, but these are buckshot loads.