There had to be something wrong - a .715 + .010" patch is not tight in a 12 bore, even if the bore was a tight .725". As a matter of fact, a .715" with .010" patch, barely impresses, only .005" per side, on a .725" bore.
Thanks for measuring.

What range? How many shots per group? 1" to 1 1/2" is very good for 50 yards. At 25 yards, 1/2" to 1 1/2" (on centres) is to be expected, even from a good smoothbore. 50 yards minimum seems to be necessary to allow different loads and loading techniques to show up on paper.

Here is the last target I shot at 28 yards(25 meters) with my 20 bore, smoothbore having .005" choke.(Imp. Cyl) I used a .595" ball with a .022" 'matress ticking' patch & 82gr. GOEX 2F. i don't know why I pulled a shot low, but without a rear sight, anything is bound to and can happen.