Several times on this forum an illustration (circa 1900) has been posted that showed the minimum barrel specs recommended at various distances based on a nominal bore of .729 (12 bore)

Does anyone have the reconmendations for 10, 16, 20 and 28 gauge? Either in illustration or written form? I'd like to get more from my wall thickness and bore gauge measurements for the subgauges and this info would be handy. (e.g. Min recommended thickness at 6-9-12" from breech)

Much appreciated!

http://parkerguns.org/forums/showthread.php?t=7889

I have this data already:

http://parkerguns.org/pages/faq/BarrelThickness.htm

Does anyone have subguage info?

The Spanish Proof House prints a leaflet accompanying Spanish guns and it contains a diagram and all the min-max internal dimensions, including chamber length, diameters for rim, chamber, cone, bore for all gauges down to 9mm shotgun.

For thickness the steel quality comes into play, the stronger the steel the less of it required. The CIP published a chart showing minimum thickness for three ISO specified steels. This chart was reproduced in various books on proof, one of which was sold by the Blue Guide.

Anyone have this CIP chart?