I have a PH Musketoon. No really good results with anything resembling the original Pritchett, better with the Lyman 575213. With Hogdon minies with thinned base plug sized to .575, 42g 3f Old Eynsford black, it'll do about 2in at 100yds. You read that right, 2in. That's after quite a bit of experimenting and tweaking the load, but these guns can be quite capable. My 1st gen Parker Hale 2 band Enfield will shoot the same way.
Smoothbore accuracy- in North South Skirmish competition, I'm shooting a 69cal 1842 Macon with a 24in barrel, so it handles very much similar to the musketoon. I'm shooting a .682 round ball with 65g 3f Old Eynsford. After tweaking the load a bit, it will put ten shots in a row into under 3in at 25yds. That sounds fantastic, but there are others shooting much much better.
If you are seriously interested in getting these guns to perform, come over to the North South Skirmish Association.
You guys should really come to the last skirmish match of the year. It's held at the Statesville range- Allison Woods on 11/10-11. Saturday we'll compete with revolvers, smoothbores, carbines and repeaters. Sunday will be the musket match.