Pete Keillor writes:

Paper shims under the single cutter were used in the Foxfire book. One
groove was done at a time until full depth, then index for the next.
I still have all the Foxfire books somewhere.

There's an excellent video out there somewhere -- albeit possibly not
on the net -- in which a rifled flintlock is tracked from wraapping &
forge welding the barrel to rifling to making the lock and eventual
proof fireing of the completed barrel. Details of the rifling
process/tooling were pretty clear IIRC.

Sadly, I can remember neither the smith's name nor the "restoration
village" where he worked for many years. Some grovelling through
blacksmithing sites or googling for terms related to restoration or
re-enactment villages might turn it up. Not in New England, more like
somewhere in Virginia?

--
Michael Spencer Nova Scotia, Canada