doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com "The Southern" chamber burst

600X SEM of the barrel wall at the location of what appears to be the initiation site. The 150X showing the cleavage is on the first page.



The cavity/void is presumed to have been the location of a large inclusion that likely contributed to the initiation of the failure at that point - slag?
Dimples are ductal overload indicators
The "possible voids" are likely the manganese sulfide inclusions seen on the 200X above, and which would diminish the steel strength.

If this is the presumed initiation point of the failure, do these characteristic seem similar to the outer barrel adjacent to what was the braze joint?

The reason I ask is could rust, that wasn't a part of the original construction, take on the SEM appearance of "slag" and possibly run along two dissimilar materials, such as the braze and barrel? The relative sizes of the potential manganese sulfide pools and the initiation point seem to indicate that "burned" steel may not have been the primary contributor. As in the past, if there was a partially, if not completely, successful braze joint, could there have been a manufacturing error in that area, that could've been hot enough to burn steel? Only thoughts.

craigd, as I recall, when the ferrous contamination was initially identified, it was consistent with the type of oxide that is produced during slow rust barrel bluing.

My gosh! The plot thickens... where do you suppose that might have come from???

In addition, it didn't seem that our great copy-and-paste shotgun barrel expert and serial blasphemer, or his metallurgical experts, had even considered slow rust barrel bluing oxide as a possible source of the ferrous oxide contamination found in the compromised braze joint.

You may also recall the Preacher giving some totally incorrect definition of "burned steel" after receiving the METL report.



We have groupies here who are actually grateful to be fed this crap.

I had to remind or otherwise inform him that temperatures sufficient to burn the carbon out of steel would be so high as to vaporize the zinc component of the copper-zinc brazing material. See my post #547631 in the thread referenced here:

https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=546106&page=9

But the verbal and pictorial efforts to discredit me go on and on... even dragging Jesus Christ himself into the fray. You could never find entertainment like this pathetic circus over on the Upland Journal forum! Dave shouldn't invite donations... he should charge admission to the Libtard Freak Show!

Craig: At the time of the burst, the barrel segment flew into some brush next to the shooter and could not be recovered. It would have been helpful to examine the burst edges (and probably would have saved having to section the barrel, which was a challenge), and maybe the presumed inclusion at the initiation point would still be present.

Slag is easily identified by EDX.

This is from the previously published Remington burst; a barrel section at 50X. The composition of the inclusions by EDX was predominantly silica, metal oxides, phosphorus, and sulfur ie. slag, and not manganese sulfide.



This is a section of a L.C. Twist barrel that broke when on the extensometer way back in the pattern welded barrel strength study. It broke at this inclusion which by EDX was slag




The barrel survived 110 years of use with the defective braze and "burned" steel. Interesting to speculate if it would have remained intact with "better" barrel steel (it is non-standard AISI 1018 low alloy low carbon steel with slightly high phosphorus & sulphur, and a low concentration of nickel) and/or without the presumed inclusion and/or the high pressure reload?

So you have all these photos and speculation about what you are looking at but where are your standards for comparisons for said conclusion? Right now you are sounding like Adam Schiff!

Do you mean sections of turn-of-the-century barrels that did not burst? A valid criticism.
METL has been pretty excited about this and the previous pattern welded barrel study because there are very few images thereof in the metallurgical literature, and almost none of pattern welded barrels.

BTW and relevant. There are images of hull steel plate recovered from the Titanic. The �acid-lined open hearth� hull plate steel, from the works of David Colville & Co., was non-standard AISI 1020, with a slightly higher phosphorus, much higher sulfur, and lower manganese concentration. The tensile strength was 65,000 psi, and the low Mn:S ratio (6.8:1) made the metal more brittle in the cold temperature.
The photomicrographs showed �dirty steel� with both silicate, sulfide, and manganese sulfide inclusions.

This is from "There's Danger in Damascus" by Major J.W. Houlden, June 1950 "C-I-L Oval", a publication of Canadian Industries Limited and reprinted in the 1960 "Guns Digest". Obviously pre-SEM & EDX and of much lower resolution



Burrard published a few photomicrographs also


Adam Schiff? Really? Why is it so hard to discuss things on this Forum without personal insults RARiddell?

The image reminds me of an image or two of damascus barrel sections that you showed. What I see is that through the drawing process, large and irregular inclusions might be mitigated by elongating their shape and offering the opportunity for favorable alignment of what might be perceived as a grain.

Here ya' go Craig. 20X 3% Nitrol etched specimen of 2 Iron crolle.
The top is the edge of the barrel segment blown out at the time of the burst and the fracture is clearly ACROSS the crolle pattern; steel is grey-black, iron silver-white. The crack appears to be in the steel alternee, or possibly at an iron-steel interface.
The straight lines in the lower right are interesting. The metallurgist suggested that they are evidence of shear deformation at the time of the high pressure burst.



These straight lines of silica within the iron strip may have been acquired as part of the rod rolling and twisting process. It looks like one in the middle left originated in a globular silica inclusion

I see that 'crack' as a success in this way. It is with the grain that was formed by the steel drawing process. By grain, I mean that the dark pools, inclusions, have been decreased in size, surrounded by sound steel that is directional.

While there may be switch backs with twisting and hammer strikes, the continuous direction of the rods are formed on a mandrel roughly opposing the direction of the barrel tube. In other words, they're arranged to form hoop strength. I'm not thinking a barrel can't fail, only that there may have been an engineering intention to the construction back at a time when the mills couldn't assure consistency.

Just conversational opinion Doc Drew, to me your various images are much more interesting than often held assumptions that damascus would look like a mess of welds. Could the straight lines be abrasive scratch patterns, either not fully removed during the sample prep or as a result of the sample prep. Slight warpage and material hardness variations could account for seeing a scratch pattern in one area and not the adjacent?

The metallurgical engineer at METL showed me some samples ready for microscopy and SEM after the machining, prep, and mounting but I certainly can't comment on the process. The staining is from the 3% Nitrol etching (other etchants are also used). I would assume a scratch would not etch differently from the surrounding matrix?