Greg: By your description, all of your guns are unaltered and in proof, and your new wall thickness gauge is coming up with measurements that are reasonable, and perhaps even typical, assuming 85 to 90 thousands is a safe minimum standard, as has been suggested. The "area ahead of the chambers" is of course imprecise and open to interpretation, and the segment between the end of the chamber, forcing cone and "regular" barrel wall, given its abrupt transitions and complex angles, is no doubt difficult to measure. That said, as long as the guns are unmessed with, and you're shooting the kind of ammunition intended for them, with loads and pressures approved by the proof house, I don't think you need to worry.
If you remain concerned, you'll probably get both more, and more specific, advice by sharing details about your guns, such as their age, make, type of steel, interior dimensions, specific proof marks, etc. TT
