Checking for cracks

[Double Trouble]

I had my ca. 1886 Parker hammer gun (twist barrel) radiographed locally, but nothing conclusive was found, even though I see something that looks like it could be a crack in the bore. I had a guy with a local boiler company video the bores with his borescope, and you could see this "crack" - but it was hard to tell if it was a crack or merely just some corrosion along the lines where the different metal "strands" meet. (This gun is old & well-used. Even the outside surface of the barrels has some of that "washboard" feel to it, so I'm sure the inside surfaces have it too.) I wish I could email the video to you, but it is a 63 MB file. I did send the barrels to Merrington, for inspection, measurement & light honing. I hoped that the honing would remove this "defect." It did not. I asked Kirk about the "crack" - and he acted like he didn't see one; didn't know what I was even talking about. (Which made me wonder...) All he kept saying (instead of a direct answer) was "If it was my gun, I would shoot it with proper, low-pressure loads." It still makes me wonder what I'm seeing, and why he acted as if he didn't notice it...

[Drew Hause]

My compliments for doing your due diligence John. I'm not aware of any NDT lab with significance experience in evaluating pattern welded barrels, and suspect it may be related to liability concerns.
It is my not particularly informed opinion that direct visualization, RT and MPI are complimentary. If MPI showed an indicator at the same location as the visible "crack" I would be apprehensive.

This is Jay Oliver's 1874 $100 grade Lifter with a fracture in the Crolle barrel probably at the rod edge "zipper" weld



A Twist fracture



Damascus-Twist fracture

[edgarspencer]

Having more years, than I care to recall, with hands on experience, in MT (dry or fluorescent), RT, LP(V), LP(F) ET, and UT, I can say that if I were heading off to a Lab (many of which are run by my ex QC Dept, I would be asking for either Visible Dye penetrant, or fluorescent dye penetrant testing.
The very nature of Twist, Laminated, or Damascus materials is very conducive to false positive interpretation. The magnetic permeability of the dissimilar materials is distinct enough to show flux field lines.


The only important part of the above, for the non techs, is highlighted. I just can't help myself.