simple the best, I made one my self, but standing vertical this way force of gravity don't influence arm and then gauge

simple is best

Just to make things interesting (and not start a war) I have taken the ribs of of several barrels as I am sure many members have and Have found them to be heavily rusted. So the conclusion that I would make is that the thinnest part of the barrel is going to be where you can't measure. That would be under the rib. Stating barrel wall thickness may be ok but I will proof fire mine.

true

but that's a you break it - you bought it deal

if you know the barrels measure thin before purchase - that expense is avoided

I might just be lucky but...Most of the ribs I have removed,were full of nasty looking flux but rust has not been a issue.
The area where the rib sits is filed to a slight flat and is thinner on most of the barrels I see



http://i966.photobucket.com/albums/a...psb8993a06.jpg

http://i966.photobucket.com/albums/a...ps749f1189.jpg

Neat Gary; another Damascus-Twist barrel.
This is David Purnell's 1888 12g 0 grade toplever hammer gun refinished by Dale Edmonds.

http://pic20.picturetrail.com:80/VOL.../305238492.jpg

Gary Carmichael's also marked "Twist"

http://pic20.picturetrail.com:80/VOL.../405274430.jpg