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Thanks for the updates. I would have originally guessed the different images might have shown more welding flaws and inclusions, but they really do look good in your samples. Though they could detect a difference between the iron and steel, once welded and twisted, it does seem like the working barrel behaves like a monosteel.

Looking forward to any tensile strength comments you're able to share.

A 500X of the inclusions; silica, carbon, junk



Burrard was a master, but the second edition was written in 1948, before compression formed hulls, polyethylene wads, the widespread use of reloaded shells, the industrial application of piezoelectric sensors for pressure testing, scanning electron microscopy (SEM), composition analysis by X-ray Photoelectron Spectroscopy (XPS or ESCA), Energy Dispersive X-ray Spectroscopy (EDX or EDS), Ultrafast laser spectroscopy, and likely lots of other stuff I don't understand.
He did mention the industrial use of MPI and radiography dating to the 30s.

Certainly. But it does make his statement that a ring bulge always indicates an obstruction all that much more remarkable.

That sweeping conclusion, circa 1930's, has yet to be proven wrong.

Microphotograph, scan, dissect, analyze as you wish.... we first saw pretty well defined evidence of a bulge just in front of where this barrel failed. We 'speculated' it was an obstruction based on Sir Maj. GRB's ancient teachings.

Drew, at his own expense and as a service to us who wish to use old guns in a safe manner, has confirmed that the old master was indeed correct.

This is a significant contribution to the art and science and history of the shotgun. Bravo again.

Drew,

Thanks again for the additional information! I'm quite surprised at the low carbon content. But as a buddy of mine often says; "One test result is worth a thousand "expert" opinions."

The linear structures are typical of the silica strings that are found in wrought iron. Globs of silica in the iron as it comes out of the furnace, are drawn out into strands when the material is forged and/or rolled into bars.

I'm still a bit perplexed by the inclusions in the "steel". I expected the steel to be a cleaner material. Going to have to think about that a while���

Steve: As we discussed yesterday, I'll be sending you and our mutual friend in Nevada the full Failure Analysis, the unused barrel segments, and what is left of the barrels used for tensile strength testing. We should have about 10 3 and 4 iron crolle Damascus pieces to play with, and the only limit to the investigative possibilities is our curiosity and rapidly being depleted bank accounts

Drew, the larger pieces of junk in your 500x photomicrographs looked similar to some photomicrographs of steel mill scale I was looking at. Mill scale could certainly be a likely candidate because it is by far the most common impurity that is found in a steel mill. Another slice just a few thousandths away might well have been much cleaner and more homogenous. Scale itself has many and varying components, dependant on the alloys in the steel. Hence, the varying appearance under magnification. Ferrous oxide, various other iron oxides, magnetite and hematite are prevalent. I examined a very thick piece of scale last night, about 3/16" thick. Surprisingly, it was very different, from the inner surface that contacted the steel, to the outer surface that was in contact with the reheat furnace atmosphere. So just the orientation within a steel sample could possibly make it look like different animals. The inner part was dull and much more granular while the outer part looked smooth and shiny, almost like blue-black glass. The outer skin had a noticeably stronger attraction to a small magnet too.

I'm sure some would look at those photos as proof that Damascus is full of flaws and weaknesses, but rolled-in mill scale is probably just as likely to be found in early fluid steel barrels.

I'm thinking that's a 'typical' sample that the lab ran into on this barrel. At 500x, I'd think those inclusions have been effectively managed. Since it came from the barrel, that sample has been drawn down to a tiny percentage of the raw starting material.

New inclusions might be introduced, but that picture does not appear to be at the surface or near a weld. Chances are those inclusions were larger, but may have been reduced and dispersed by the extensive forging.

Here is a 50X of the inclusions Craig and Keith



I do not believe Adam has found any voids, contrary to Damascus mythology

Drew,

Do you need a set of lower grade Belgian twist barrels? I happen to have one, I was going to use it to test refinishing processes. It's one of those that are stamped "Laminated Steel" but I think it's really twist. Would you like all or part of it?
Ken

Thank you Ken, and PM sent.