AA#2 is very close to Bullseye in burn rate but cannot be substituted grain for grain......Never substitute. I found Bullseye loads for the 12 ga way back when I had a surplus after quitting commercial loading of revolver/pistol ammo.
Most shotgun powders are quite fast burning but again, none are interchangeable.
Use the data books the companies put out or buy some Lyman or other manuals.
I keep all of them, sometimes have to go back and look through some that are years old.