Welded barrel seams

The recent DOM and Damascus discussions got me to thinking about the seams in these barrels. With DOM, you have a single seam, either butted or scarfed, for a total welded seam the length of the barrel. With a twist barrel, you have multiple ribbons welded in spirals, and an astronomical increase in total welded seam length. Has anyone ever figured the actual seam length in a 40-inch twist barrel? We must be talking something like 50 FEET of welded seam -- and a vast increase in the potential for spots of seam failure.

A spiral seam is not subject to the same kind of stress that a longitudal seam is. That is why damascus was better than the normal straight seam barrels of the day. Pressure is against a longitudal seam. Very little pressure is against a spiral seam.

Excellent point, Jerry.

jerry huddleston said:

Pressure is against a longitudal seam. Very little pressure is against a spiral seam.

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Since pressure in a closed space is exerted in all directions equally, why would this be true?

Spence

Because pressure is in PSI. The only pressure that is exerted on a spiral seam is the aea of the breach plug or the bullet face. Say a 50 cal. Breech plug face equals .196 square in.
But the pressure on a longitudal seam is the pressure exerted on the barrel walls. A .50 bore has .785 square in pr 1/2". so the pressure on a longitudal seam is about three times as great as a spiral seam. These figures are not exact but only illustrate the difference in porportions.
This is the same reason barrels fail more likely than breach plugs

Pressure in the barrel at ignition is exerted equally in all directions, barrel walls, breech plug, longitudinal or spiral seam. In the same way that a spiral seam has more length than a straight one in the whole barrel, it also has more length in the area where the pressure is exerted, so is exposed full pressure along more length than a straight weld.

I don't understand your reasoning that says the longitudinal seam gets three times the pressure.

Spence

I restored a very rusted barrel on a Danish-Norwegian 1774 musket. Before browning the barrel, I polished it down and etched it with hydrochloric acid. What appeared looked very like a damaskus like pattern but is probably due to the barrel being forged out of used nails. Try imagining the total length of welding

George
The walls of the barrel have many more sq. in. of area Than the breachplug or the face of the bullet. Fot a spiral seam to open up the barrel must stretch lengthwise. It's a matter of square inches of surface that pressure is exerted on. Outward pressure in the barrel walls is not direct pressure on the spiral seam but it is on a longitudal seam.

I understand what you are saying about the walls receiving more pressure because of their larger surface area. When you consider the seam, though, you seem to be thinking it would be opened by the walls trying to flatten out, in effect pulling the seam apart. There would certainly be that force, but I don't think that's the only way a seam might fail. Direct pressure on the seam itself could "punch" a hole in one spot while the rest of the seam remains intact and the walls don't move. Spiral seams would offer much greater length for that to happen.

Theoretically.

Armchair engineering is sometimes fun, but it rarely solves anything, for me. Because I have zero technical training along this line, my personal experience counts more, and since I have shot a lot with both DOM and damascus barrels without a hint of failure, there's no help there for this question

Spence

The seam area itself is so small there just isn't enough pressure on it to blow a hole in it. There would have to be an existing hole in it or a flaw to cause that. That is why touchhole liners usually don't blow out. The area for the pressure to push against just isn't large enough.
The pressure limits of a barrel are figured a lot different than one might think. You can't just mutiply the area times the pressure and figure out the limits of a gun barrel according to the tensil strength of the material. The limits are figured by what is called hoop strength. I don't know enough math to do the formula. It is extensive for a heavy walled cylinder.

jerry huddleston said:

There would have to be an existing hole in it or a flaw to cause that.

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Exactly. I assume you would agree that a well crafted weld won't give under ordinary shooting pressures, either straight or spiral? It would be the seam with a poor weld, and the more seam length there is, the more chance there is for a spot of poor weld.

We each have to decide for ourself what we think is important in making a choice of barrels. I've decided that the modern machine welding process makes a barrel with an extremely small chance of a flaw. If mine blows up then I'll know I decided wrong.

Spence

The debate here is not weather anybody cares if you blow yourself up. We are debating if a welded tube of unknown type steel is as safe as a solid bar of known type steel that has been bored out so that some here can make a more informed choice. The fact remains that the stress is not the same on a spiral seam as it is on a logitudal seam. It doesn't matter if you believe it or not.
The statement below is from a engineering book, It is about what I have been trying to explain to you. Even if you don't believe it it is still a fact. The only barrel I ever knew about personally that blew up was from a welded tube sold as seamless steel tubbing.

This is all I can say. I am going to teach my dog algebra. See ya later.

I can't interpret all that, Jerry, but I can see that your description of longitudinal stress seems accurate. Your conclusions about spiral seams being under less stress would then also seem to be accurate. What that means for the actual in the field safety of DOM barrels I haven't a clue, and I've seen no evidence produced by anyone to help me figure that out. So, this seems a good place to call it quits.

I will say that I don't understand your personal hostility in these discussions. I guess you stay friendly as long as no one dares question your opinions, hey?. In my book opinions are made to be questioned, but only as a way to dig out any truth that's there, not as any kind of attack. We probably don't agree on that, either.

Spence

George said:

I guess you stay friendly as long as no one dares question your opinions, hey?. In my book opinions are made to be questioned, but only as a way to dig out any truth that's there, not as any kind of attack. We probably don't agree on that, either.

Spence

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The problem seems to be that you are disputing facts with opinions, at least thats the way I am reading this.
Somebody is presenting facts for safety sake and you present personal opinion.

You brought a "c" league game to an "A" league professional.

Spence. I really didn't mean to sound hostile. That's one of the defects of not talking face to face where you can hear the tone of someone’s voice. I was not trying to tell anybody what to buy or not to buy. I just want to see the truth about gun stuff out there so everyone here can make a informed decision.
The question was asked why a damascus or spirally welded barrel was not more dangerous than a tube with a straight seam weld since a damascus barrel had more weld seam.
So there's the answer. peace. For the record I have a gun I built about 35 years ago with a tube barrel. It's a 11ga. fowler. I proofed it with 300 grs. of ffg and 6 oz. of shot 3 times. I don't shoot it just because it's a relic of mine. I Since my late friend Jim wolford blew one up I just don't want another one. I have studied all this stuff for over 50 years and still don't know it all. I guess I never will.

ApprenticeBuilder said:

Somebody is presenting facts for safety sake and you present personal opinion.

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What facts are those you are thinking of? Yes, the question in this thread concerns straight as opposed to spiral seams, but this conversation has been going on for several days over about 3 different threads, the original question of which was the safety of DOM barrels with longitudinal seams. A whole bunch of opinions have been expressed to the effect that they are unsafe, but no pertinent evidence that I'm aware of has been presented to back them up. If tubular barrels with longitudinal seams are inherently unsafe because of the engineering principles presented by Jerry, then millions of guns made over several centuries were unsafe. Jerry's engineering principles are undoubtedly true, but so what? Do they indicate such barrels are unsafe? Of course not, if enough strength is built in to compensate, to keep the stresses below threshold.

Safety is a marvelous thing, but declaring DOM barrels unsafe on general principles when bunches of guys are shooting them in perfect safety is not logical.

Finis.

Spence

George said:

ApprenticeBuilder said:

Somebody is presenting facts for safety sake and you present personal opinion.

Click to expand...

What facts are those you are thinking of? Yes, the question in this thread concerns straight as opposed to spiral seams, but this conversation has been going on for several days over about 3 different threads, the original question of which was the safety of DOM barrels with longitudinal seams. A whole bunch of opinions have been expressed to the effect that they are unsafe, but no pertinent evidence that I'm aware of has been presented to back them up. If tubular barrels with longitudinal seams are inherently unsafe because of the engineering principles presented by Jerry, then millions of guns made over several centuries were unsafe. Jerry's engineering principles are undoubtedly true, but so what? Do they indicate such barrels are unsafe? Of course not, if enough strength is built in to compensate, to keep the stresses below threshold.

Safety is a marvelous thing, but declaring DOM barrels unsafe on general principles when bunches of guys are shooting them in perfect safety is not logical.

Finis.

Spence

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Seriously!?! Really!?! you should re-read this thread and your answers.

:shake: :idunno: :youcrazy: :yakyak:

In my younger days we made a lot of pipe bombs from thin-walled tubing (before the world turned all paranoid) and the fragments I recovered afterwards were rarely split along the seam. Modern automated welding creates seams just as strong as the rest of the tubing.

The problem seems to be that you are disputing facts with opinions,

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Man do I know some people that do that, usually when discussing religion :shocked2:
I used to play with steam engines and boilers quite a lot and we always figured a long small diameter boiler would take much more pressure than a big diameter one, PSI is the key. :thumbsup:

I am sorry if feelings were hurt in this thread. I will not start any more threads having to do with welded single-seam barrels on this site.