Yes - Pretty sure it is for a belted ball. The reason I wanted the rate of twist, was to see if it would be worthwhile purchasing.

If in the 3foot to 4foot range, I don't think I would be very much interested, but it has more interest in 4' or 5' twist rate, though. At 4', it might be possible to use as much as 120gr. of 2F, which would work on NA game quite well.

According to Forsyth, many English Gun makers added the belts to the common-for-the-day fast twist rates to attempt to get the gun to handle heavy loads & not strip due to the extra "purchase" in the bore. He noted they fouled excessively and would not shoot well due to the rapid rate of twist and required light charges not suitable for the range of game they were designed for.

This is why I suggested a short conical - which would have to have wings cut in the mould to fit the grooves.