Jim: any industrial NDT lab could x-ray the barrels, the problem is in interpreting the findings. No standards exist for radiography of pattern welded barrels, and x-rays can not differentiate between defects within the barrel wall, and pits on the interior surface.
Some information may be found here
https://docs.google.com/document/d/1...vwLYc-kGA/edit
It has been my hope that a NDT expert with access to testing facilities, and doublegun interest, might develop a pattern welded barrel evaluation service. To my knowledge that has not yet occured.