doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com The Southern Chamber Burst Gun

Now then, if you were to include the pre existing condition of a large area of corrosion, how would this play out?

At some point the pressure found bursting the chamber an easier route than the, or what once was, that huge "16ga tunnel" it had been using for 100 years.

Porosity spot on the dark area.

I am in agreement with 775. There was a pre-existing crack/break, where the barrel was milled for the barrel extension, at midchamber. That point is clearly shown in the picture as having previous corrosion while the rest of the fracture surface is fresh metal. This, in my opinion, is the root cause. Whether there was an obstruction to speed it along is to be determined. That missing chunk of chamber would be nice to evaluate.

John

John, it certainly would be nice to see the outer surface of the missing piece. Somehow it let go along the braze joint, so either it was a bad braze or there was corrosion - at least that makes some sense to me given what we have seen so far. I think the dark spot on the break would be confirmed on the other piece as well. I think this gun was doomed at birth, but we may never know.

Now, that's no way to talk about the Preacher and his thin skinned sensitivity over someone retaliating for his prior personal attacks. Seems like Drew can dish it out, but he can't take it. He should have thought about that beforehand. But it's easier for him to cry and play the victim.

I still wonder what good accurate wall thickness measurements are for someone like Drew, who actually thought that chamber lengthening would result in GREATER WALL THICKNESS at the end of the recut chambers??? All the measuring instruments in the world are just wasted on someone who isn't smart enough to interpret the data. But if you copy and paste enough photomicrographs and stuff from sources who really are knowledgeable, you might fool people into thinking you are a big-time expert in metallurgy or barrel burst analysis.

Sherman Bell didn't need Metl or any other Metallurgical testing firm to tell him that it was excessive pressure which caused the bursts in his Damascus barrels... or that the barrels finally let loose at the thinnest and presumably weakest point. Heaven forbid we should simply rely on common sense and things that are plain to see.

That does appear to be where the initial fracture took place. Similar in that respect to the gun Bell subjected to gross overpressure (load in excess of 30,000 psi, if my memory serves). It blew out from the void between the barrels where the extractor rod rides. An obvious "weak point"--but not very weak in that gun (a vintage Parker), given that it took that much pressure to result in a catastrophic failure.

The only failure I've had a chance to look at (a few minutes after it happened) similarly started at a weak point. The gun in question was a Fox, which has slender rods (or guide pins?) on the outside of the extractor, riding in channels just below each barrel. A friend, looking at the gun with its blown right chamber, pointed to the void where the pin rides, thinking it was a flaw in the metal. And it very clearly blew from the outer edge of the barrel inwards, toward the rib, rather than from between the barrels out. Just part of that particular gun's design, but also an area which is weaker, thus vulnerable to failure if there is significant overpressure in the breech area.

Ah William. Once again the blind hatred is making you appear the fool.
In the hope of learning something 2 of the barrels used by Sherman Bell, with the technical support of Tom Armbrust, and published in The Double Gun Journal Vol. 10, Issue 4, Winter, 1999, �Finding Out For Myself� Part II and Vol. 16, Issue 2, Summer 2005, �Finding Out For Myself� Part IX were given to the pseudonymous Zircon, a metallurgical engineer, who posted �Contribute Junk To Advance Barrel Strength Knowledge� on two public internet forums in 2005 requesting vintage barrels for composition and strength testing. By 2006 he had accumulated almost 40 samples, both Fluid Steel and Pattern Welded. Part of the collection included the Damascus barrels from the Parker GH and the Vulcan Steel barrels from the Parker VH that had been the subjects of Bell's destructive testing.
Both guns were subjected to sequentially higher pressure loads at about 2,000 pounds/square inch (psi) increments. The GH testing started at 11,900 psi and one chamber ruptured at 29,620 psi. The VH started with a Proof Load of 18,560 psi. Both chambers bulged at 29,620 psi and ruptured at 31,620 psi.

A formal Failure Analysis was proved to the BOD of the PGCA, with photomicrographs and Energy Dispersive X-ray (EDX) Scanning Electron Micrographs, but to my knowledge it has not been published.
A partial report was placed on a Public Domain forum, and is worth reading
http://www.familyfriendsfirearms.com/forum/archive/index.php/t-55364.html
The mode of failure of the barrels is not necessarily applicable to our subject barrel since the failures were induced by higher and higher pressure loads, but the fluid steel barrel failed by abrupt brittle rupture, and the damascus barrel by low cycle fatigue with ultimate ductile fracture.

and what Larry said
"On the two old Parker barrels, there is a screw hole that comes up from the bottom and pins the extractors in place. Both barrels failed at that hole, because it takes a (segment) out of the side of the chamber and is the thinnest portion of the chambered area."

I communicated with Zircon in February 2008 regarding his Analysis, then again in 2015. He still had the barrel samples and intended to do composition and tensile strength testing, and also intended to submit his Failure Analysis on the Parker barrels for publication.

"Things that are plain to see" commonly are not what they appear to be, and we all "see" what we want to see.

BTW: have you purchased a wall thickness gauge yet? Looking forward to a bunch of end-of-the-chamber numbers for our knowledge base.

The "porosity spot" might look like this; corrosion stress micro-fractures

This Parker chamber blow-out was presumed to start at the screw hole and extractor guide channel
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=491058&page=5



And the point of a failure analysis is to avoid the same, which Savage must have missed. As of 2018, lawsuits related to the Savage 10ML II (designed for use with Smokeless Powder) with Crucible 416R Chromium Stainless Steel barrels were ongoing. It is alleged that catastrophic barrel failures have been the result of both a design flaw (screw hole) and a metallurgical flaw (manganese sulfide inclusions in the 416R)
https://cases.justia.com/federal/appellate-courts/ca6/12-1475/12-1475-2013-08-09.pdf?ts=1411028258