doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Has anyone ever had a damascus barrel blow up

I have only been around two blow ups on a trap field and I have been shooting for 7 years and both were re loads and of course modern guns. When I was a kid one of the few family guns was a Damascus S/S not sure maker but my grandfather's gun, probably a low end Birmingham gun and we shot everything in it from super X high brass dove loads to buck shot which I would bet was 3 drams. Never had a problem but sounds like we were way above what we should have had in it.

Sir Gerald Burrard, The Modern Shotgun, Volume 3, The Gun and The Cartridge, �The Diagnosis of a Burst� 1948

"In the case of an obstructional burst the really essential evidence is the ring bulge. If there is a ring bulge, there must have been an obstruction; and the absence of a ring bulge is conclusive proof that there could not have been an obstruction."

"A pressure burst can only occur in the immediate neighbourhood of the chamber; and so if the burst occurred ahead of the chamber cone an excessive pressure can be ruled out. But if the burst occurred at the breech, and was the direct result of a high pressure, confirmatory evidence will be found in the appearance of the brass head of the cartridge which caused the accident. For it is utterly impossible for a very high pressure to be developed without it leaving its mark on the fired case."

Burrand identified an indentation of the extractor on the case head, enlargement of the case head, flattening or fracture of the rim, lifting of the primer from the pocket, flattening of the primer against the breech face, and deep striker indentation, especially in comparison to shells of the same batch, as evidence of excessive pressure.

There are several formula for bursting pressure, esp. Barlow's
P=2 S t / D
P=Bursting pressure in psi.
S=Tensile strength of material in tube wall.
t=Wall thickness in inches.
D=Outside diameter in inches.

Barlow�s refers to a pipe capped at both ends with a static pressure (a pressure cylinder). Shotgun barrels are not designed to be pressure vessels as one end is open and the pressure rises and falls quickly.

While working on an article regarding a chamber blow-out and the formal failure analysis, I discussed bursting pressure with a metallurgist and a mechanical engineer. Both were of the opinion that we do not have a formula for shotgun barrels (non-pressure cylinder). The various hoop stress formula are helpful but again do not predict bursting.

Wallace H. Coxe, in "Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics" published by E.I. du Pont de Nemours & Co. in 1931 cites a study in which a fluid steel barrel was cut to 9� and capped, then a series of progressively increasing pressure loads fired. The barrel cap was blown off and barrel burst at 5,600 psi.

I also found a study by the Royal Military College of Science, sponsored by the Birmingham Proof House and the British Association for Shooting and Conservation, showed that an obstruction by 2 fibre wads (total weight of 4 grams) was sufficient to bulge or burst a 12g barrel shooting a 28 gram (slightly less than 1 ounce) load. Peak pressure occurred 22mm (.866�) past the leading edge of the obstruction.

Burrard's protocol for the diagnosis of a burst

In order to give the investigator every possible chance of arriving at the truth the gun should be sent up for examination as soon as possible, and without being cleaned. Accompanying the gun should be the fired case of the cartridge which actually cause the burst; if possible the fired case of the round immediately preceding the burst, a few fired cases, and as many unfired cartridges as possible�of the batch which was being used at the time.

With this evidence available it should be possible to diagnose the cause of the accident with certainty. By far the most common cause of burst is some obstruction in the bore, and so the first thing to do is to look for evidence of an obstructional burst, that is for a ring bulge. If a ring bulge is detected the cause of the burst becomes established beyond any shadow of doubt.

Every effort should be made to try to ascertain what the obstruction could have been; and in this connection the owner of the gun should be asked to give replies to the following questions:

1. Was the accident caused by the first shot of the day through the barrel which actually burst?

2. If the accident was not the result of the first shot of the day, what was the result of the shot from the barrel which burst immediately previous to the one which caused the damage?

3. Did anything in the least abnormal occur in the case of the shot fired through the burst barrel immediately before the round which caused the burst?

4. Was the chamber apparently empty when the gun was opened for re-loading (prior to the burst)?

5. Was any member of the party using a smaller bore of gun? What size?

6. Does the shooter own a gun and cartridges of smaller gauge than the one which burst?

7. Under what conditions was the shooting taking place?

8. What was the nature of the ground on which the shooter was standing or walking at the time of the accident?

The answers to these eight questions and the actual position of the burst in the barrel should between them provide sufficient data to determine the nature of the obstruction with comparative certainty. But the fired case of the round which caused the burst and also that of the round immediately preceding the burst should also be examined for confirmatory evidence.

In order to complete the investigation a most careful examination should be made of as many live cartridges as possible from the same batch. Some should be opened, and the weights of the powder and shot charges checked in order to test for regularity of loading.

Then all the remaining cartridges should be tested for ballistics; that is pressure and velocity, and if possible recoil.

Then a most careful examination should be made of the fractured edges (and) the thickness of the wall�
(This is where the formal failure analysis and metallurgical study starts).


Wernher von Braun "One test result is worth one thousand expert opinions"

Burrard also discusses the bulge in an obstruction of this nature occurring forward of the location of the obstruction. Briefly his explanation was that when the load hit the obstruction it moved it down the barrel but velocity was checked enough the expanding powder gases behind the wads "Piled Up" to produce a local high pressure area. The barrel could be bulged or burst depending upon the severity of the Check in velocity.
He also mentioned that tests were done with both solid & hollow obstructions & the severity of the bulge or burst was totally dependant upon the weight of the obstruction, thus eliminating the theory that obstruction bursts were caused by Compressed Air between the load & the obstruction.

Good discussion here
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=357105#Post357105

And if I might rant for a moment

2-3 times/year between this and other forums, someone reports a blown up gun/barrel, might post a few poor pictures, and the usual experts (including myself) pontificate as to etiology. The OP and the remains then disappear and we have no follow up and are no smarter.
To properly diagnose a blow up requires a formal failure analysis and metallurgical study, by an experienced examiner, and costs about $1500 done right. But unless a personal injury lawyer gets involved, it won't happen, and if the case goes to litigation, we'll likely never know the results.

I believe however that MOST vintage gun barrel ruptures can be diagnosed simply by looking for a bulge and measuring the wall thickness. How hard is that?

Remember the first Parker Sherman Bell blew up in the destruction tests he reported in DGJ? Blew in the chamber area, basically peeling out from the hole for the extractor rod. I saw a Fox with a similar pressure failure, but it peeled from the outside--because on a Fox, the guide rods for the extractors ride in small channels on either side rather than between the barrels. Obvious weak spot in both cases--"weak" being a very relative term, since it took 30K+ psi to blow Bell's Parker.

I think in extremely thin barrels a split will occur before a chamber failure with or without any obstruction. The payload is in effect an obstruction and pressure behind it can cause a barrel failure. We are talking about very thin barrels or worse barrels which are thinner on one side than the other. Hoop stress only work if there is no difference from one side to another. If one side is .025 and the other is .015 I would expect more failures along the thinner area.

The only chamber failure I have seen was due to reloader error. Gross over charge of powder. The two barrel failures were due to snow/ice or mud. Guns were in duck blind, factory ammo, both guns had end barrel failures with ring bulges. Most likely one was ice in the choke area. Never know for sure.

Years ago my old friend Oscar Gaddy with the help of a noted authority did failure tests on a Parker Damascus gun. Long story short it went to 30,000 psi before it blew! These tests were covered extensively in Double Gun journal and lead to todays expanded us of old Damascus guns. I wish my old memory could pull the main author's name up because he did far more than a Parker and in fact di some real junk guns with safe results.
Dig out the articles and be surprised.
bill

It's worth noting that in all three of the blown chamber incidents I have personal knowledge of, the gun provided feedback before the catastrophic event.

They were all the result of defective shells. No mystery as to the cause in any of the accidents.

1. 11-87 turkey gun (brand new) fed shells loaded by accident with 36 grains of Green Dot and 1 1/2 oz. of lead shot. It withstood the first shot. The turkey was still flopping around... so.... "the bolt was very sticky, but I was able to chamber the second round by cycling the bolt manually". Boom.

2. Lanber O/U fed the first products of a very young man's reloading efforts. Trap shooting with the bottom barrel. Several very loud reports, difficulty opening the action, yet he persisted and nobody stopped him. Boom.

3. The aforementioned Italian made, very well regarded, and almost new O/U. Recently proofed by Italy at over 18,000 psi. Sporting clays. New shells, imported from a CIP compliant country. After shooting the lower barrel, the gun was very difficult to open. This was attributed to the 'newness' of the gun. Next, shot... Boom.

Note the pattern. The gun gave a warning in each event that something was wrong. We can learn from that.

I have been around thousands of rounds shot in Damascus including myself. NO. The only three that I have seen or have personal knowledge of were a Browning O/U GTI with factory WIn ammo, a Mossburg pump with factory ammo that my friend had just bought at Walmart and a unnamed double all with steel barrels.
Another incident that I near forgot. When I was in my mid 20's, I decided that I needed a cleaner powder, so I loaded my ML Shotgun with some 2400 powder. Needless to say the nipples blew out just over my head, but the barrels were intact and I shot it for many years afterwards with BLACK powder.