Albert: you might review this document
https://docs.google.com/document/d/1...A/edit?tab=t.0
There is a list of testing labs about 1/2 way down.
There are industrial NDT labs all over the country but very few do barrel proof testing.
Most modern makers use a combination of mag particle or ultrasound, then pressure testing, to SAAMI or
CIP standards.
You could easily spend >$1000 on radiography, mag particle testing, ultrasound and proof testing.
Almost all of us who use vintage barrels, both pattern welded and fluid steel, do so after the bore has been examined for pits or defects using a bore scope, and the wall thickness, from breech it muzzle, is examined.
Then with shells that reproduce the ballistics of the loads the makers recommended, being cautious regarding recoil in light of the >100 year old wood.
Oz. of shot and fps are the primary factors to consider; not pressure.