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

But it is so much more fun to make definitive diagnoses with the least amount of data...

In the meantime, the rib extension to barrel bond looks anything but very strong. How much is corrosion vs. just a poor job, I can only guess.

Thank you JHJ. We'll take it one step at a time.
Metallurgical testing labs make the big $s diagnosing pipeline blow-outs and airplanes falling from the sky. It is possible that one of the METL engineer could perform one stereo macroscopic examination and explain with some certainty what happened just for the cost of a consultation fee.

Miller, the word that has been used in reloading literature for decades, when referring to a reduced charge of slow burning powder in a large capacity case that causes damage, is detonation. You may not agree with the terminology, but that is the term that has been used to describe it for ages. It may be an incorrect usage of the word, but it is what has been used for as long as I can remember to describe the event.

So, your issue should be not as much with our usage of it as much as with the original writers who coined the phrase. We're just ignorant enough to continue with it.

SRH

So just what do you think the missing piece could tell us that the photo of the very thin section doesn't already show?

It is highly doubtful that a chamber lengthening reamer would have enough lateral force exerted on it during a minor lengthening process, to create the thin area.

Since there is no other pitting or corrosion apparent in the remains of the chamber, it is highly unlikely rust or corrosion was involved. More likely... The chamber was probably thin from the beginning, and that thin area just happened to include a small inclusion of rolled-in scale. It happens, and should be a stark reminder that our fluid steel isn't necessarily homogeneous and free of internal defects, just because we can't see them. Even the best steel mills in the world, with excellent quality control, sometimes make scrap. Sometimes that scrap makes it out the door. Metallurgical testing of the remaining 99.9% of this blown barrel might not reveal another hidden defect.

It seems apparent that there was also some prior leakage of powder gasses due to this combination of defects, and that was causing a separation of the rib braze joint. When enough surface area of the braze joint was compromised, it finally let loose. It seems unlikely this barrel was ever proofed with a double the normal pressure load, or it probably would never have made it out the factory door. But it is likely the braze joint added enough strength to this thin area for all these years to contain normal chamber pressures. The tensile strength of a good braze joint can approach the strength of a welded joint. I think that short section of rib was essentially a patch over a thin and defective area that finally failed.

There might be a fair chance that something was machined out of round, the groove for the rim of the shell does not look uniform. Any old pictures of the chambering setup during manufacture? If the rim recess was cut with the chamber reamer, some other secondary machining very well may have been done in there.

Still, I'd think that if there're signs of pitting in the chamber towards the rib, one might wonder if the hoop strength in the area is affected, knowing it starts off relatively thinner.

why not just measure the barrel wall thickness of both barrels in front of the chambers and post that data here?

Great idea Ed. Since the Preacher argued several weeks ago that chamber lengthening in vintage doubles could result in GREATER WALL THICKNESS at the end of the recut chambers, maybe they got so thick that it actually created an obstruction!

Sheesh! Maybe we should all donate to collect $1000.00 for failure analysis, and continue to make a mountain out of a mole-hill, when the cause of the burst is pretty apparent.

I think it's reasonable to guess that the defect progressed, fresh broken steel or brazing would be bright.

I wouldn't think this is propellant gase damage or coloration. The location would seem to indicate that a hull would seal against the chamber wall. This pit, or defect, or inclusion would have had to have been past the 2 3/4 in. hull length. Also, I'd think if gases came back along the rib extension stub like the darkness suggests, the shooter might see fouling on the breech face and rib extension.

Stan;
With all due respect that's not the way, I read it. When this phenomenon first began appearing many "Suspected" detonation. It was ultimately "Proven" that it was not a detonation, but indeed was a pressure spike from an obstruction, the bullet being fired is the obstruction.

The only difference in this from sticking the muzzle of a shotgun in the mud & firing it, thus blowing the end of the barrel off is in the latter case the powder has all been burned, though the gas is still expanding. In the case of the rifle, it occurs so near the breech that the powder is still burning as well as the gas expanding. In Neither case though does a detonation occur.

I simply Refuse to use the Wrong term when I "KNOW" it is wrong as that only serves to propagate the Error..

Edited quote from BrentD




Think you hit the nail on the head, why ream out a chamber, also just looking, but the tear appears to be angled, I would be surprised if when measured the walls are as thin as they look!