I had one their Kentucky percussion models and the bore was under size between about .002" -.003". It's recommended to use a smaller diameter .433 round ball. But they're reputed to be fairly good shooters with 4 groove rifling and a slow 1 in 66" twist rate.
My 1st flint is an Ultra HI.
It was a kit gun and I had to harden the frizzen to get it to fire.
I use a .437 round ball W/ .010 patch. I can shoot this rifle all afternoon with a spit patch and never have to run a cleaning patch down the bore.
My 8 year old Grandson loves to shoot this rifle. He likes a 40 grain load of 3Fg b/p.
here he is shooting at a 75 yard paper target and doing well