I am of course saving some good stuff for the articles
but now have MPI and radiography on 2 barrels and radiography on another. Having difficulty digitizing the hard x-ray films with adequate resolution however.
Thought I'd remind us all of some of the 'expert' opinions expressed here and other Forums:
“Because a Damascus barrel is pattern welded and one can readily see the welds, both MT and PT would be useless for surface examination.”
“…magnafluxing would show a perfect Damascus barrel to be FULL of flaws.”
“A good magparticle technician can examine a set of barrels and find abnormal indications, usually indication of a "crack," "slag inclusion," and whatnot. They can also give you a qualified opinion on how likely the indication is to cause problems later on. They can find these inside the wall of the tubes, not just on the surface.”
“If you are concerned about the state of your barrels with regard to fatigue there are many materials labs scattered about the country, manned by ‘experts’, that could do some simple penetrant tests and other visual inspections for you to put your mind at ease.”
“And there is nothing wrong with good ole' RT, or x-ray. Yes, there will be tons of lines on the film due to all of the welds, but again, a good technician can find indications there.”
Industrial NDT has an almost 100 year history, with abundant science and academic research. HOWEVER, there are NO industrial standards for the interpretation of Pattern Welded shotgun barrels, NO published images (to my knowledge) and NO experts in interpreting radiography because no one has looked at enough to be an expert. Pattern Welded shotgun barrels are not oil pipelines SO we are all trying to understand exactly what we are seeing by both MPI and (especially) radiography.
I had a long and illuminating conversation at the Jan. Las Vegas Antique Arms Show with a gunsmith from the Northwest that routinely does MPI on Pattern Welded barrels, and has found exactly ONE unsuspected crack. The gun was a higher grade British maker's and the owner declined destructive testing to confirm the crack.
Jason graciously donated a c. 1902 Syracuse Arms No. 0 'New Twist' which sadly was the victim of an attempt to lengthen the forcing cones, and 16g short magnums. Both chambers still 2 9/16" but the MWT at the end of the right chamber is only .087; left was .110. At 3 1/8" from the breech there are four 1/4" -3/8" bulges; at 2:00, 5:00, 8:00, and 10:00. This one has a crack
A view of the bulge at 5:00 (top left of image)
MPI shows a crack extending inferiorly from the bulge
Which is not seen on radiography, so is it only superficial? I think the lucent (less dense) lines at the second 'V' represent the barrel segment welds and not cracks
About mid-barrel
MPI shows more likely cracks. Wall thickness there is .040" and no bulge by my bore gauge
But again radiography is negative for cracks, but the film does show what are very likely interior wall surface defects (pits), which is a major limitation for radiography
A different gun and image with many lucent areas likely to be pits rather than defects within the wall
Anyway - may need to have Adam dissect the areas so we REALLY know what we are seeing.
And the barrels were already unusable, so did MPI or radiography add anything (other than $250 to TEAM's bank account)?
Just like a MRI of a spine, interpretation requires an expert pair of eyes, and expertise requires looking at LOTS of digital images. I don't think anyone in the country has the expertise to interpret Pattern Welded barrel radiography at this point. BUT we've found lots more neat stuff x-raying the barrels
and I'm hopeful that I can get better resolution of the digitized x-rays through a photo processing outfit here in Phoenix. Gee, I guess that will cost $ too
Thoughts?
