Yesterday several of us Vermonters visited the new owner of a mid-1800s rifling machine. This is from the Hilliard shop in Cornish, New Hampshire. The machine utilized a single spiral cut groove in steel tubes to give the twist. Twists from 1:26 to 1:72 or so were possible with the available guides, and 6, 7, or 8 grooves.
I’d seen most of the tools snd cutters and such before. However the twist drills used to bore barrels out were new to me. They were tapered twist drills with aggressive, forward-facing cutting edges. Take a look!