I haven't shot round ball, patched or naked, from smoothbore musket but I have shot round balls from a Pedersoli 12 ga. side by shotcup. These were naked 0.690" round balls sitting on top of hard card and/or felt wads. Accuracy was non existent! Balls hit randomly around targets at even 25 yards. All you have to do is look up some of the info on smoothbore military muskets using loose round balls and you will find out how poor the accuracy was. 50 yards was generally considered the maximum range that a naked round ball (military loading) could be depended on to hit a man size object.
The old military muskets were loaded with round balls considerably under bore diameter to allow "windage" and easy/fast loading in fouled bores. Precise accuracy was not expected as smoothbore musket fire was generally used as volley fire.
A bit of reading material:
https://bowvsmusket.com/2015/03/01/m...y-at-80-yards/
https://scholarworks.iu.edu/journals...d/19841/25918/
There are a number of smoothbore musket shooters that report quite good accuracy to 70 yards or more using patched round ball and I have read of smoothbore shooters using patched round balls winning blackpowder matches against rifle shooters out to 100 yards.
I have shot lots of round balls from a modern 12 ga. shotgun with varying results. A loose fitting round ball can obviously bounce down the bore and can easily roll so picking up random spins from the bore friction on one side. With loose round balls accuracy was about the same as with the muzzleloading shotgun... essentially non-existent. However, with a round ball somewhat larger than bore size or and undersize RB in a shotcup with good fit, accuracy to at least 50 yards can be very good as in 3" to 4" groups. Much beyond 50 yards in my experience groups start to open up quite quickly and by 100 yards groups are undependable and ranging from 8" to 12". While this is opinion, I think it is common opinion in that the round ball, even launched with no spin at all, seems to pick up random spins from air drag so that groups become exponentially larger at longer range due to the "knuckle ball" effect of random spins which I have seen referred to as "trombone" trajectories.
So, the short story is, in my opinion anyway, that your patched round ball shot from smoothbore should provide good accuracy to at least 50 yards, reasonable (hunting level) accuracy to 70 yards or even further but groups will start to open up and get larger quickly with with increased range due to random spin of the ball induced by air drag on little imperfections.
Probably more words than you wanted. Oh well, I talk too much!
All my opinion only.
Longbow