doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com The borrower had to know......

Shotgunjones mentioned these were good tubes, and I agree. I think you summed what might be going on. While it may(?) not be their fault, the barrels did fail. I believe all gun barrel steels are considered 'soft'. The lucky thing was that it failed slowly, and signs showed that it was probably closer to it's ultimate limit than before the bulges.

The problem with being good tubes is the commentary is completely ignoring the thickness of the tubes. What's the point of having a barrel thickness gauge if the only requirement is to check barrels for obstructions and being alert to signs that an obstruction might have occurred, such as a squib load.

I think the British proof houses are plenty evidence that good tubes going in to the test, don't always come out the other end as good tubes. The point being that if obstructions aren't part of the test, then 'relatively', I think obscene, low over pressures can damage gun barrels.

If it were my money buying a gun with 'original' barrel and bore specs, I think I'd expect the barrel patina to nearly obscure the damascus pattern. Maybe, the bore would be a little frosty in likely places. Refinishing gun metal is supposed to remove 'negligible' amounts of metal, but I don't think that is always so.

If(?) no obstruction were present, then there seems to be little point to worrying about 'reasonable' over pressures. We seem to worry about over pressure when every thing is going well. Some metallurgists will say that the metal in the bulge is likely stronger now. Why not tap it down and call it good.

Miller is wise.

But an identical double obstruction...

You don't suppose do you....

That this was a 28/16 accident?

Doesn't work that easily, at least not for me. You can't remove the bulge between the ribs, and by the time you have tapped the bulge outside the ribs down the ribs have popped loose. Removing bulges is wasted time, IMO.

SRH

Burrard made the point that an obstructional ring bulge usually occurs 3/4� to 1 1/4� beyond the leading edge of the obstruction, and is invariably associated with lifting and bending of the rib. (which I do not see in the images)

I think, the more rare a gun, the more hoops that are worth jumping through to get it fixed as close to original as possible.

I was thinking that while cold working might technically increase the tensile strength of the bulge area, the comment about good tubes had to do with the ductility that the barrels showed. That characteristic would probably be lost around that area.

I hadn't noticed, in the pictures, a lifted rib or signs of cracks in the forearm wood either. It doesn't mean anything, but it might be supposed that this is not a 'ring' bulge.

Bro' Drew.
Your photo is not a bulge. It is a rupture. I don't see lifting and bending of the rib in the gunsunlimited picture, but, that doesn't mean it isn't there. Also, an obstruction in a bore is just that, until it isn't. An obstruction that clears miliseconds before yield is met will cause a distortion to some degree, if not a rupture.
Pure arm chair quarterbacking from here in cyberspace. But, interesting, anyway.


Best,
Ted

I think Sherman Bell measured wall thinning in the area of bulges. I don't think the thinning would return to the original wall thickness after "tapping" back into place.

Experts on Guns and Shooting George Teasdale Teasdale-Buckell 1900
http://books.google.com/books?id=4xRmHkr7Lp8C&pg=PA373&dq
On the subject of steel v. Damascus, Mr Stephen Grant is very clear, and much prefers Damascus for hard working guns. He related an anecdote of one of his patrons, whose keeper stupidly put a 12-bore cartridge into his master�s gun without knowing that he had previously inserted a 20-case, which had stuffed up the barrel. Fortunately, no burst occurred, but a big bulge, which, however, Mr Grant hammered down, and the gun is now as good as ever.


1902 16g No. 0 L.C. Smith. Chambers extended to 2 7/8" with wall thickness at the end of the chamber of .096"



Looks pretty thin on radiography



But the MWT at the bulge was .102. Bore in bulge was .680; 3 1/2" .660" with WT .114"


Sad 12g Smith 4E with nice Chain Damascus with two bulges



The biggest bulge was at 4 1/2" with bore at 3 1/2" .735" and at the bulge .758".
Wall thickness at 3 1/2" was .118, 4" .092", in the bulge at 4 1/2" .078", and 5" .073".
4 1/2" non-bulged barrel was .090" and 5" .080"

Those wall thickness you cite on the Smith's there Drew are certainly adequate. These as well as the one in question all still have the appearance of an obstruction.
We certainly have to remember that Teasdale's thoughts were written in 1900. Most steel barrels of that time were made with a very low carbon steel, on the order of a 1008 or 1010.
It did not take the industry long to begin upping the carbon content to something on the order of 1040 & soon going to alloy steels with other elements which increased the strength.
With the possible exception of those very early low carbon barrels any pressure which would bulge or burst a "Good" steel barrel would do likewise to the finest Damascus ever built.
I say this as a great admirer of Damascus, but their "Beauty" is not in their "Superior" Strength.

It's not so easy to find pictures of proof house failures, but the CIP does have a short video, in the 'proof' category, of failures. The reason I use that as an example is because a proof house, particularly if they show it, should have followed their procedures in which the barrels were fully measured and inspected prior to firing proof loads. In other words, free of obstructions.

Anyway, most of the shown failures appear to be twelve gauge guns, and chances are they would be thought to be obstruction failures. One picture in particular shows a 'banana peel' muzzle, lowest barrel pressure(?), blow up. Chances are the first thought would be someone stuck it in some mud or snow.

Maybe the topic gun was an obstruction, maybe not. A side thought on 'tapping down' a bulge. Material would have thinned when it was 'stretched' to a larger surface area, but the material is still there. Not likely at all, but theoretically it could be returned to where it was originally. Finishing would likely take more off, but if decent thickness remains, there're probably some unique guns to make the attempt. It's probably more common to raise a dent, the same thing in reverse.