Good stuff, Curly.

If testing patches or sighting, oft times I pick up the old patches and indeed, use them again, in my 14 bore rifle.

I call my .69 a 14 bore & it measures 9 1/2 pounds, as well as having a bore .003" smaller than true 14 bore size. I use either a 15 bore ball (.677" in WW or pure) or the tighter fitting .684" ball in pure lead. I use the same .025" patch(mic. compressed) for both. They are quite tight with the larger ball, but both are reusable for a number of shots. I once shot a 5-shot group off the bags at 50 meters, using the same patch for each shot, simply re-lubing it each time. The charge then, in 1987 or 88, was 165gr. (6 drams) 2F.

That rifle shoots best with a bit more powder than your smaller 16 bore will likely need, but still shoots passably with a mere 110gr. to 120gr. 2F. It just does better with more powder.
Your groups look fine for a DR- but going up 10 to 20gr. might be even better.

I think Dan P. stopped at 140gr. of 2f in his 16 bore single barrel flinter, showing 1,700fps and good accuracy. I also think he was using Swiss 1 1/2F.

If you are shooting a sub 16 bore ball, I would not call it a 14 bore. 16 bore, of course is .662" and 14 bore is .693", nominally.