Try shooting at large sheets of paper next time out. Shooting small targets will not tell you much. Your patterns may be centered far off of the 10" predrawn circle targets. A good many shotguns, regardless of make, will not shoot true to the bead. Chokes can have very different POIs from the same gun as well.
You can buy contractors paper in rolls 35" wide x 140' long at hardware stores, Home Depot, or Lowes for 10-12 bucks a roll. Shoot, then draw your circles around the most dense portion of the pattern. You may find you need adjustable sights.
Have a good one,
Reloader