Marrakai - thanks for posting your test results. 10" at 100 yards is excellent accuracy from a round ball. It is also better than I've ever got with facotry Foster slugs from a Police Riot gun.
: My double used to do a bit better than 10". I used hard balls, and the base cups off a shot-cup for centering the ball in the bores. Worked for me. Differing powder charges as in working up rifle ammo also helps. Picking a load and putting up with the results doens't work with either rifle or shotgun, not if the best possible results are required.
: this is why my next tests will be with the lower part of a steel-shot cup. They are thicker and are considerably more heavily built.
; We've a long way to go as every gun is a law unto itself.