I've known and seen this gun for over a decade. It is one of the best and was owned by a good friend here in Alaska and now is owned by another friend in the lower 48. It is one of a pair that sold about 12-15 years ago (if memory serves), shoots very well. It has slow twist and is made for a 1400-grain round ball. Chamber size is a 4, bore size is a 5, proofed as a 6.
Cheers,
Cal