Those 'bands' definitely show obturation, for sure.
If they expand to the bore, they should be launched as a knuckle ball in baseball and maybe make the same up and down
oscillations in the same manner, but likely at a slower pace (if they do fly like that), up until they take on a spin and veer off the original line of flight.
Longer range accuracy from a smoothbore, is definitely a function of initial velocity, I can only assume.
The most accurate shot in our club with a smoothbore shooting balls, is a fellow with a left handed (see-cheating right off the bat) Penn. 20 bore he built
himself from a Chamber's kit. He uses a snug patched round ball and 85gr. 3F - at all ranges. It is tough to beat him on our coarse when I'm shooting a rifle
& impossible if I'm shooting my smoothbore.
Taylor is the second best smoothbore shot at our club and he also uses a patched ball, but with 85gr. 2F.
I've said a couple times I need to test the hypothesis of higher speed with patched balls, as well as the undersized balls and heavy charges of 1F, but just haven't
gotten a-round-tuit.