You didn't mention the temperature when you patterned.
Something's i have learned from this site and applied have proven as effective
as claimed. Deep cleaning a bore and choke, temperature effect on patterns,
choke dimensions to bore diameter.
One thing that seems overlooked and pointed out
by our more knowledgeable contributor's is allowing a choke to break in ! I see chokes for sale
in the classified's that are only fired three times or less.
I observed a pg 690 improve gradually over
thirty rounds fired. Also saw a dramatic improvement with a lightly polished 720 choke that performed
so poorly when new i considered it a lost cause. Also noted early on that mass produced ammo was
inconsistent enough to convince me to handload all my ammo.