Huntschool,
An interesting thread and questions you raise.
Re accuracy, I think the small calibre smooth -bore needs more powder to ball than a heavier ball does, as the light ball does not 'set up' as well when fired.
I am thinking of the Olympic smooth pistol and long gun results here, where most are small bore and the targets shot would put many rifled arms to shame, but see no reason why a smooth rifle of small bore should not shoot well to 50 nor 75 yards at least. After all, small -bore rifles do not shoot as well at 100 very often, as do the larger calibres. (say comparing a .32-.36 and a .50)
If I had a .40 smooth rifle, I'd feed it 70 -80 grs of powder, so as an old mate says, "the ball gets to the 10 ring before it realises it was shot out of a smooth bore!.
When playing with a musket of .760" bore, firing a .750 ball with a wad and no patch, (125 grs 2F) Recovered balls showed a definite equator where they had expanded to fill the bore.
To get the same to happen with a light ball would take a decent amount of powder and no small charge will do it.
Please pardon the rambling.
R.