Claybuster CB1138-12.
IMO/IME it is the most versatile wad for loading 00 buckshot. Wade Rush/Bubba Rountree Outdoors likes it too.
To the OP...Pattern testing with different loads and different chokes in your shotgun is the path to buckshot nirvana. The one load you tried from the BPI Buckshot Manual that your shotgun didn't like might be a laser in somebody else's shotgun.
No shortcuts to performance.
Just my .02,
LeonCarr