On Wed, 23 Oct 2019 20:25:55 -0700, pyotr filipivich
wrote:

"Steve W." on Wed, 23 Oct 2019 18:18:13 -0400
typed in rec.crafts.metalworking the following:


At the moment I'm thinking a wooden bench then a single slotted bar and
an adjustment pin system at one end to select twist rates. I made a
smoothbore .50 a long time ago and it shoots real well considering. The
bench and the rest are the easy parts. The big thing is the cutter
advance, current thought is a long tapered wedge with a fine thread
adjustment.

I recall reading about using paper or similar thin shims. But the
wedge with fine thread might work too.

May not be automatic at first but I'm not running production
levels.

For real fun, work out how to do a "progressive twist" - where the
rifling twist gets higher the further down the barrel the bullet goes.

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.

Pete Keillor