doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com THAT was close

Jager: can't confirm that, but at the failure analysis the metallurgist can tell the difference between rapid ductal failure (plastic deformation with both tensile overload and shear) and fatigue failure (striation 'waves in the sand').

It should be noted that thin walls alone should not be blamed as the cause of long barrel splits, or other failures. In the Preacher's photo above, we see what are generally considered "thin walls" all along the barrel split. But note that we see wall thickness dimensions ranging from as high as .027" and no less than .019"... and these numbers are AFTER stretching to the point of rupture has occurred.

If "thin barrels" was the cause, then someone has some explaining to do. Assuming these barrels have been fired and survived many hundreds or even thousands of shots, why did the failure take so long to happen? Since we see a fair number of Flues guns with fairly thin barrel walls, it's safe to assume those walls were just as thin 10-20- or 50 years ago.

Common sense would dictate that there had to be some combination of factors that led to the presumably sudden failure. Perhaps it was a light obstruction such as a wad or snow in the barrel. Maybe there was some internal flaw or inclusion in the barrel steel that held for decades, but finally let loose with a single round that produced slightly higher than normal pressure. Something may have scored the inside of the bore creating a stress riser that became the initial point of failure. We don't know if this barrel suffered any prior damage such as a dent, or even what the temperature was when it failed. We can all engage in guessing games, but with the information we have, nobody really knows. Metallurgical testing might shed some light on it, or maybe not.

What we do know for certain is that there are many thousands of guns with even thinner barrels than this that are still being used with both low pressure and standard factory field loads. But they have not had this sort of rupture happen. The Preacher himself has stated he owns an O grade L.C. Smith with Damascus barrels that have a thin spot measuring around .016" at roughly 14 1/2" from the breech, as I recall. Yet those considerably thinner barrels have not failed even though the thin spot is closer to the breech where pressures are presumably higher. The Preacher uses low pressure loads in this gun, but many other guys are blissfully firing any old factory load through guns that have barrels with points just as thin, or thinner.

There are many factors that may determine that a barrel will fail under normal use. If it was a matter of barrel wall thickness alone, there would be no need for any sort of factory or government mandated proof testing. All that would be needed is a minimum allowable barrel wall thickness. I'd bet the London or Birmingham Proof House could tell us about a great many barrels that failed proof even though they had what would normally be considered very adequate minimum wall thicknesses. Unfortunately, steel is not some homogenous monolithic substance of 100% consistent purity and identical properties. In a sense, I suppose we could safely say many barrel failures occur because of thin barrels relative to the pressure they were exposed to and other factors.

In the 70’s apparently “fatigue” followed by inevitable failure was a “fact” among a segment of the shotgunning public. Thomas, in his book of that period, “Shooting Facts and Fancies”, speaks to the concern in a section entitled, “Do Guns Tire?” and references an enquirer’s concern that a “considerable number of old guns … were coming to the end of their life” due to fatigue. He quotes a “well known” shooting writer (whom he leaves unnamed) who supports this position, “Metal tires with age and use, and becomes subject to fatigue.”

Thomas’ answer? “That is putting things in the woolliest possible terms, and as a general statement is simply not true.”

“… it is not age that induces fatigue in metal, nor is it use, as such, but only repeated stressing above the fatigue limit.”

“The thing that limits the safe life of any good, honestly-made gun is not the fair wear and tear it has had, but outstandingly the abuse or neglect it may have suffered.”

And in conclusion …

“The number of guns of all ages and grades that fail in normal service, other than those that have suffered abuse or neglect, or improper repair or some obstruction in the barrel, is utterly negligible, and the possibility of their so doing is well inside the margin of acceptable risk.

So herein is our dilemma. We may be able to see signs of neglect or abuse but we can’t “see” how the 100+ year old arm that we are shooting was stressed. We can’t know the internals of the metal used in that specific gun. And the designers and makers of these guns themselves didn’t know the fatigue limits of the guns when they made them.

So as I currently await the arrival of a “new” Damascus barreled double I can’t know what it’s experienced in its 121 years. I can only thoroughly inspect and measure it once it’s in hand and then make a determination as to whether it falls within my own “margin of acceptable risk.”

More mythology
https://doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=190762&page=1

Rocketman
"Age (chronological time) embrittlement is not an issue with plain carbon steels such as used in older fluid compressed steel barrels, twist, and damascus. Fatigue embrittlement would require millions of cycles at the level of strain which barrels in good condition experience with firing."

Never have I saw a damascus or twist barrel split similar to that one. Have only seen maybe 6 pics of failed damascus. Have seen several dozen fluid steel like this over the last 50 years. I would be surprised if anyone could produce a pic of 3 sets of blown Damascus in same pic laying next to each other. Go ahead make my day!

Thanks for the empirical examples, Doc. I was just flying "seat of the pants" according to my experiences with bursts and ruptures in other applications.

I believe what a lot of people think is that steel will become brittle because of the heating then cooling of the metal. And this can happen to steel, but it has to reach a temperature of about 750-1100 degrees fahrenheit and then cool. Probably several times.

Late to the party here but..are we certain that there was not some obstruction in that Flues tube? Maybe I've missed something but most of the destroyed shotgun tubes that I've ever witnessed personally (& thankfully not experienced) were caused by a wad or dirt or even snow (which is what wrecked the last 3-inches of my brother's 16 Nitro Special back in the late 1970s).

Embrittlement arguments have been around for a long time and yet they've never been explained in a way for me that is convincing. There are many really old automobiles and even aircraft still in use that would also be subject to this malady and yet they are still in operation.

I’ve queried the seller but thus far no response.

So…helped Doc Drew catch scent of this one and hoping he can come back with something.

Actually Lloyd, automotive engineers have determined that steel body panels change over time. Autos are designed with so-called "crumple zones" and other features to absorb the impact from a collision while hopefully keeping the passenger compartment fairly intact. The body panels come out of the stamping press dies with some work hardening which makes them springier. But the engineers have found that some of this springiness dissipates after a few years of driving, probably due to the slight springing and vibration a vehicle endures as it is driven for thousands of miles. Actually, it's just the opposite of becoming more brittle over time, and it is something that can be measured and even seen in the microstructure of the steel.

However, while this is true of the alloys used for auto body panels, it may not hold true for other alloys of steel. I agree with you that the Flues barrel that is the subject of this thread was probably split open due to some sort of barrel obstruction. The relatively thin barrel walls certainly provided a weak point for them to let loose, but the same gun was probably used for a very long time with the same thin barrels, without so much as a slight bulge. If the owner of the gun was available to tell us the barrel split on the first shot after honing out some deep pits, I might feel differently. But a lot of shotguns are being used with even thinner barrel walls in that region. There are a lot of variables, and it is naive to merely blame the failure on wall thickness alone.