Do not claim to be God's gift to reloaders, but Bullseye is among the fastest burning pistol powders made. It is NOT listed as a shotgun powder by Alliant in their tables. Cannot help but feel you are courting disaster using that to drive an ounce of shot- shotguns operate at an order of magnitude difference of pressure. Red Dot, Green Dot, Clays, etc were made for shotshells. Bullseye was not.
What we have heah is.... failure to communicate.