Jeff's son is operating the business now as Jeff has passed.
In the picture the rifling appears to be slightly more than .004" however, that is really not that important.
Your round ball, however, should be groove diameter, not bore diameter, if used with normal card wads.
A bore diameter ball or even one smaller can be fired accurately, as long as the wad is groove dia. The wad, if cupped, will hold the ball in the middle of the bore and give it rotation for accuracy.
30" is VERY fast for around ball of that size. It may shoot just fine with a light charge, such as 4 drams (110gr. 2F).
I used black powder in plastic hulls to good effect.
If the hulls have paper base wads, those will have to be dried after cleaning. An oven tray with oven at 180F will dry them quickly.
Wash them with a brush under water, or with a piece of maroon scotch bright held in hemostat pliers. For a case that size, needle nose pliers would also work.
30" twist makes me think it is designed for slugs, but that greatly increases the recoil and shock to the stock.
I think you should test it with 4 drams, maybe maximum of 4 1/2 drams and 2f or 1F. No 3F, and no substitutes. If must use a sub, then T-7 would be the only one that is not harmful. A load of 3 to 3 1/2 drams would be max. imho.
REALLY good looking bore.