doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Repair of Bulged Barrels -- Can You -- Should You

I need the benefit of some expert experience. Have slight bulge about 15 inches from breech on one barrel of an old Superposed. Not a ring bulge. Ribs do not seem de-laminated. Do not know the history of the gun, or how the bulge was produced. Can it be repaired? If so how. Should it be repaired? Any comments on resulting strength of such a repair if it could be done. Is this all that much different in concept than repairing a dent. Any recommended gunsmiths for this repair? Thanks

Before I state my opinion let me say that I am not an expert, or even play one on TV on which bulges should be repaired and which ones should be left alone.

But as a rule I feel that a bulge in the first two thirds of the barrel are bad news. Have a bulge repair fail in the last ten inches of the barrel and no great harm can come to the shooter. Have it occur within a few inches for your face or hand and you might not be so lucky. If your load is 10,000 psi at the chamber it may be 6-7,000 at the bulge and only 2-3,000 near the choke. Easier to deal with thin or weak metal near the choke area than in the middle.

Stretched metal is almost impossible to compress back into the proper place. Most bulges, I think get more filing to make the flush than is smart. Very minor bulges might be repairable but why risk it?

The only sure way to know is to send it to a very good barrel man. Mike O would be my choice. If he thinks it will not be safe he will tell you so in a fast second. His work and prices are super and he can get to the job faster than anyone else I know.

No--No.

15" sounds about where the barrel taper straightens out. The typical shotgun barrel has two tapers that are blended as best as possible by hand.

When metal is cold formed, it hardens and toughens up a bit. A bulge or dent is cold forming. The more working, the more hardening and toughening...to a point.

Hard steels cannot be easily formed or may not yield (form) without fracturing at all if exceptionally hard. Nothing ground breaking here, I have a tremendous grasp of the obvious.

Formable steels have limits of how much they can stretch. The softer the steel, generally, the more it will stretch. But, there are alloys that stretch more than others of similar hardness.

Generally, shotgun barrel steels are relatively soft and form easily. That's why they bulge and dent readily. That's why then can be fixed as well.

The ultimate "bulge" reduction in a barrel is a rotary hamberforged barrel. It starts as a short large diameter bar with a large hole and is literally hammered until it shrinks in diameter and grows in length. Tony G showed me his rotary forge machine that he hadn't implemented yet, but planned to.

A bulge should be assessed by a knowledgeable gunsmith. Frankly, I don't know how they gain the knowledge other than someone taught them and so on, but someone undoubtedly fixed dents and they didn't or did fail and they learned from that and passed it on.

But, one thing that is not so subjective is doing a crack inspection. That can be done visually with strong magnification or with enhanced NDI methods.

Frankly, from your discription of "slight bulge" I would say the metal will be plenty strong after it is formed back or reduced. That's not to say it can be fixed, given there is a rib on top and another barrel below.

I'd give a trusted gunsmith a look at the barrels for an assessment.

I agree with Chuck. The bulge is almost certainly the result of a small barrel obstruction.

You do have a serious problem....I'd say you have a wall-hanger.

In my opinion a gunsmith that would try and hide that in a shotgun barrel has no scruples and comparable to a guy that would torch color an action.

I agree with the guys that go to length to advise you.
As this is not a gun that has a history with you or a family member, it may or may not be worth the cost of repair. That is unless it is on the low side of cheap and in nice condition otherwise.
There is always the possibility of tubes and shooting smaller gauge shells.
Regardless of whether it is successfully repaired, it is still greatly lower in value.
Just some thoughts.
Best,
John

Unless it's one of those high grade models these things are "dime a dozen" so why bother fixing it. Look, even if it's possible to repair it, how much confidence are going to have while shooting it. I would not have much that's for sure.

While realizing we all prefer perfect "Cosmetics", one other option is to simply shoot it "As Is". It is really doubtful it would affect the pattern much, if at all. I did sucessfully repair a buldged bbl once, but it was on an auto-loader & just behind the muzzle. "NO" I did not consider myself in the same class as a "Torch" guy, as I in no way considered this a dangerous repair.

If he keeps shooting that thing is there any doubt that bulge will eventually open up rather violently? It's called a barrel BURST for a reason.

The difference between a dent and a bulge is vast. Most dents are easily raised and unless extreme in size or have a sharp crease in the metal not be a problem. A bulge is a stretching of the metal in the exact opposite direction and the one which all the stress is being exerted when the pressure builds. Think of it as an aneurysm of the barrel vs a slight collaspe. I will take the slight collaspe as the repair and result are much more predictable.

If you still want the gun buy a set of Briley tubes for $300.00 and shoot it in small gauges.

Jm - yes, there is great doubt that a simple bulge will ever open up! Since it has been cold worked (by the gas hammer that made the bulge) it is actually stronger than the surrounding metal. If done with some skill, it can be made to go back in place with only a bit of cosmetic polishing. "Shrinking" is a common sheet metal technique and shotgun tubes are in the same thickness range as sheet metal and of similar composition. The question here should be, "Can it be done economically?", not "Can it be done safely?" If it isn't economical to fix, then he can most likely (affirmative opinion of gunsmith with gun in-hand needed) shoot it as per 2-pipe.

If the bulge has a crease, the we have a differing issue. I'd estimate from the typical published pressure vs displacement data that the pressure in the 15" from muzzle area will range from 1500 to 2000 psi. It would be easy enough to calculate the hoop stress if we had the wall thickness and bore diameter. That will give a good indication of safety factor.

I see no difference in repairing a bulge vs a dent. A dent is only a bulge to the inside.

For you guys that think any bulge is unsafe, think about all the cold formed parts that you come in contact with in regular course of your days in which your safety relies. Many auto parts that critical to the structure are cold formed. Thousands of aircraft parts in which you place your trust are cold formed.

Jon,
While a bulge in a barrel may resemble an aneurysm in a blood vessel, the materials of each are entirely different in their properties both before and after the bulge. The typical barrel material is a fairly mallable steel.

As for a bulge, especially a "slight" bulge ever openning up, I'm with Rocketman. If you were to test the steel in the area of the bulge, assuming it was not cracked, it would be harder and stronger than the other area. If it were, indeed, "slight", I'd have no reservations of having it reduced or even leaving it as Miller suggests. Some of you may recall the Rem 32 with the bulge that several knowledgeable members were after recently.

I agree (strictly my amateur opinion, no official expertise) with Chuck on this and would like to add that the pressure 15" from the breech is going to be relatively low. The Dupont pressure curve chart that I and many of us have saved, shows less than 4000 psi @ 10". 15" will be somewhat less than that.
Superposeds, while pretty reasomable, are hardly a "dime a dozen". Get a real expert's opinion and go from there.

You might send the brls/gun to Art Isaacson in MO, 636-944-3630. He's seen many 1000s of Superposed.

Don, Jim, and Chuck are on the same wave length. This is not rocket science and the pressures are not off the scale. Find a gunsmith to fix the bulge and strike the barrel to make the repair disappear. End of story, except shooting the gun. I can show you dent and bulge repairs that would make your eyes water if you saw the "before" pictures. So can most good gunsmiths. Go for it.

If it is a nice gun and you really want to shoot it, yet you are uneasy about shooting it "as is," then why not send it to briley and have them fit it with a set of tubes?

Actually, if it is a 12 ga. gun, you could have 3 sets of tubes fitted, one each in 20, 28, and .410 and, given that it is a good quality gun, you would have a skeet setup that is as good as it would be sans bulge......

The short story is "Get someone competent to pound in the bulge because the gun is not going to blow up. End of story." All this "Watch out, you'll die" is BS.

I'm not sure anyone here thinks it will blow up.

I agree with KY jOn....dents are one thing bulges are another.

Homeless, I think you said exactly that when you posted "You have a serious problem. You have a wall hanger." Bullship! If you want to say that a guy has a problem that can't be fixed, don't deny that you said that later on. You said it and it was not correct. I think his gun can be repaired.

I have a superposed in my shop now that blew out the bottom barrel about 2-3 inches if front of the forend. No missing pieces just a big hole. I saw this gun about 12-15 years ago and it was only slightly pregnant then. I didn't think it would cause any problems so I told the owner to keep shooting it. I don't know how many rounds were fired before it blew out. Some day when I get caught up I'm going to try to repair it but first I'm going to talk to some experts about repairs. I measured the wall thickness when it came in and I think it measured a little less than .025. Pretty thin. Bill

Bill, it is unfortunate that the gun you mention blew up, but the fact that it is a Superposed and the fact that it was pregnant 15 years ago may be red herrings. We just don't know for sure.

I shot a 16 Fox for years that had a visible bulge about half way up the right tube. I imagine I would be still be shooting it if it hadnt been stolen. I also noticed the ol Joe went from "cut it off for a cowboy gun" to shoot it as is...I just dont even bother reading his comments anymore, skip em...

FWIW, I have a 28ga O/U with a bulge in the lower bbl forward of the forearm that I have been shooting just that way for over 40 years. I have not had it repaired because the bulge is uniform, meaning it is the same all the way around the innner periphery, no point in having it pounded out cosmetically when it would still have a 'bump' inside on the top. I don't wish to have the ribs removed & all that, to fix it correctly, the side ribs remain tight and the bbls are quite sound & 'ring' nicely still. Pattern were not affected in the least; it is IM/F. 28's are generally loaded to higher pressure than the larger gauges. The gun has seen thousands of rounds through it since the bulge.

I can't say as I have ever personally seen a bulge that only affected the visible portion of the bbl., but it is likely safe enough as is or repaired by a competent gunsmith & either way I doubt there is any reason to look back.

edit: I also had it examined at the time by a smith that I considered to be more than competent & those were the choices he presented. I elected to leave it alone.

Repaired....to your satisfaction not mine.

My Parker T Hammergun circa 1885 had a nice bulge on one barrel when I bought it several years ago. It was about 12-14 inches from the Breech. I peened it back slowly with a backup inside the barrel. Cant tell it now and I have shot it many times since.
I suspect the Old timers did it a lot as practicality was the order of the day

Sell it to Bill Murphy and buy yourself one w/o bulged barrel.

I'm going to look over Gargantua able to digest loads containg up to 4&1/4 drams of powder. It's got 30" F/F barrels, 3" chamber, raised matted rib, and juicy Browning vent pad with white spacer. It's bigger gun then my 201e and Sterlingworth combined. Just the thing for my Kent TM and Bismuth 1&3/8oz semi-mag loads. That's not a "dime a dozen" piece.
It was made in Liege 20 years before I was conceived.

Someone said it quite well...

A bulge is just a reverse dent. Bulges are reduced by careful and judicious peening all the time. Check for a crack, have a knowledegable barrel man work on it, and get on with the program. Or shoot it as is. Or get it tubed. All viable options.
Another would be to get the damaged barrel sleeved.

At 15", the pressure is in the neighborhood of 4500 psi and some change, extrapolating based on the Dupont curve.

Kirk Merrington can do it, or Mike Orlen.

Regards

GKT

I've been shooting a Darne R10 that has two pimple bulges in the left hand tube, for well over a decade. It has seen some hot loads in the past, but, usually doesn't anymore, as it is my prefered grouse gun, and I don't need hot loads in those woods.

The maker, in St Etienne, examined the gun, and told me to shoot it as is. Inspite of a healthy backbore some forgotten gun plumber did in the past before I got it, the minimum wall thickness on this gun is .064. There is a reason for that-it is a 65cm barrel gun, and in order for them to get these guns to balance well, heavy tubes, and an under-rib (uncommon on Darnes, usually) were used. Since the gun was a post WWII example, the steel was pretty good stuff as well. No worries, here.

Some bulges, matter a whole lot more than other bulges, it would seem, and it might have more to do with the rest of the barrels, than the bulge itself.

My point, long way around, is this-someone who knows something about shotgun barrels, and has the tools to examine all the details should have a look at it, and pronounce it fit to use as is (like my example, above) based on some measurements and knowledge of the gun. Kirk Merrington is a good example of someone who is more than capable of this.
Best,
Ted

Yup, fix it and shoot it, as Ted and many other posters have suggested. It is not junk and does not belong over the fireplace.

"Bulge" is typically used to refer to a convex/raised deformation of a material relative to the viewing/reference surface. "Dent" is used to refer to a concave/lowered deformation. An outside bulge viewed from the inside of the barrel is a dent and an outside dent viewed from the inside is a bulge.

The outside bulge usually gets there when a bore obstruction causes a gas hammer that raises local pressure high enough to create a local force above the elastic limits of the steel. The bulging of the steel raises the elastic limit of the steel (cold working) and drops the local pressure (increasing volume for the gas to expand into) which drops the local force. When the gas pressure drops back to atmospheric upon exit of the ejecta, the local area of the bulge is not able to return to original dimensions due to being plastically deformed.

An outside dent usually gets there by the barrel being struck against a hard object with sufficient force to exceed the elastic limit of the steel in the area of the strike. Metalurgically speaking, the steel doesn't care if you think it is a bulge or a dent. The steel only knows that it got stretched more than it can stand and it is not going to "snap back" to original dimensions. To get it back, you will have to apply sufficient force in the opposite direction to overcome the new strength just enough to return it to original size and shape. Thus, the return force is usually a series of smaller, carefully controlled and more localized forces rather than one force as was the first deforming force; tap it back in place.

The hazard here is that very sharply deformed metal may not go back in place exactly. Examples would be a dent formed by a sharp edge that "creases" the metal or a bulge that has a sharply defined perimeter. In these cases, the metal may have used up much of its fatigue strength and later fail under uormal flexing (a shotgun barrel expands in diameter each time it is fired). A skilled repairman will have a good feel for how the metal is reacting and if it will behave itself in the future.

We have been reminded before that a bulge usually stretches the metal resulting in a somewhat thinner wall thickness in the area of the bulge where the dent does not usually end up with such a stretched area. However, the stretch and the amount of thinning may be very minor and is capable of being measured when pounded back into place. A review of the inch by inch pressure measurements done by Sherman Bell some time back may also give us a clue about whether we are in a significant pressure area or beyond.

I got Austrian made hammer gun with damascus barrels of 12g. Barrel thickness was o'key, but there were 7 slight bulges on both barrels. I hammered all bulges in it's place back using cooper plugs and shot this gun couple years before sold it.
Light bulge 15" from breech sounds o'key for me, but I'd fix it before sell only.

Hmm, might just be me, but, damascus would seem to be a whole different kettle of fish, then either a Superposed (Browning variety) or, come to think of it, my post war Darne. Damascus, being a lamination of several metals, might have different issues with bulges, or dents. No sure what hard and fast rules would apply. Perhaps marrying the NDT technician's daughter would be in one's best interest?

I know some of you guys love 'em, but, I've stayed away from damascus, and will continue to do so in the future. Not interested in them for everyday use, and that is the catch with all my guns, bulged or not. I'm a SAAMI spec kinda' guy, I guess, save my old Tobin 16. Eley VIPs have been a good load for that old gun, with it's heavy wall steel tubes. Who was "Demoya" anyway?

One Easter egg hunt for ammunition is enough for me.
Best,
Ted

Ted, as soon as damascus is lamination of two metals, iron and steel, bulge could be the reason of small cracks within this bulge. If not, bulge could be fixed just like that.
What about fluid steel, it's a bit more complicated, but I know for sure, if fixing the bulge needs torch heating, stay away from this gun.