doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Wall thickness measurement

Dewey Vicknair's blog
https://vicknairgunsmithing.blogspot.com/2020/03/mechanical-wall-thickness-gauges-are.html

DeFelsko PosiTector UTG P1
https://www.tequipment.net/DeFelsko/PosiTector-UTG-P1/Ultrasonic-Thickness-Gauges/

Steel measuring range 0.008" to 0.475"

Dewey is free to his opinion, but documentation that the newer ultrasound devices are more accurate than the pin and gauge tools would require comparison of both techniques on multiple barrels.

When Bill Henry made my tool, he also made a standard segment of .038" thickness with which I could 'zero' the gauge, and could (and do) recheck frequently during the measuring process. If my gauge has been set to the .038" 'zero', repeatedly measures the wall thickness at the same number (say .045 at 9"), and when checked is still set at .038" I believe the measurement is accurate. Flexing of the round support bar does not seem to be relevant to the relationship between the pin on the bar and the pin of the gauge, unless I contact the barrel wall with the bar.




The use of Ultrasonic NDT is an entirely different issue. Scroll down about 1/2 way here for a summary and links
https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/edit

I can't comment if the new high resolution US devices can detect defects within the wall of fluid steel or pattern welded barrels.

The problem with RT is in differentiating surface defects (pits) from defects within barrel



A few smiths and NDT labs have examined pattern welded barrels, but there are no industrial standards for the interpretation of those tests.
Both MPI and RT might be helpful to show microscopic through cracks in a pattern welded tube.
Obviously a great deal of research would need to be performed to determine if US can find hidden defects/voids/inclusions in pattern welded tubes, but the industrial money is not in testing a few vintage shotgun barrels.

Bottom line: if you want assurance as to the safety of your barrel, beyond a bore scope exam and expert wall thickness measurements, have them proved at a pressure of 1 1/2 X the pressure of the load you intend to use. And there are testing labs in the U.S. that will do that.