I can tell you what I use for Blue Dot buckshot loads (12 #00s).
Winchester AA-type 2 3/4 hulls.
Two (2) .135 cards.
Winchester primer.
37.5 grains Blue Dot.
No shot cup.
You might also e-mail Alliant (Hercules) and see if they have any suggestions or recommendations. Their website is at
http://www.alliantpowder.com571 has been discontinued for quite a while and I never had any specific buckshot loading data for it. 12 #00s are just under 1 1/2 ounces, and an old Winchester loading manual lists these loads for 1 1/2 ounces and 571. Buckshot will work fine, if itll fit. Maybe remove the petals?
All in Winchester AA-type 2 3/4 shells.
WAA12R wad, Winchester primer, 36.5 grains 571.
RP12 wad, Winchester primer, 36.5 grains 571.
WAA12R wad, CCI primer, 35.5 grains 571.
Ive never tried 571, so those are just from the book figures.