Rob, That is the very most classic fowler barrel transition and I've filed many a sixteen side to make a Getz fowler barrels look like that.
I dove into the archives long enough to find a copy of the American Fowler Brochure (four 8.5x11 pages, front and back covers shown - circa 1989, base price $3650). I built ten of these guns, originally planned to build twenty with my youthful optimism. My apologise for the sidetrack... BTW: I also did the entire brochure, except printing back when layout and paste-up meant scissors and glue.
