doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Barrel ring bulge revisited

The recent resurrection of Tony�s thread re the 20 ga Clarke got me wondering about bulges again. I�ve read (ie, Shotgun Technicana) that any dent must be repaired because a dent is a form of an obstruction and therefore dangerous. On the other hand, I�ve read that many barrels with bulged barrels are safe to shoot, depending on whether the bulge is in a low or high pressure region. This brings me to my question that I�m hoping an experienced gunsmith or metallurgist will try to answer. What to do with bulges close to the breech? Close to the breech is a high pressure area, a likely unsafe area for a bulge. I�m assuming a bulged barrel in this area is unsafe to shoot, but is a bulge in this area amenable to repair? It seems to me that once the metal is actually stretched after reaching its elastic limit, it�s molecular structure is forever changed. I�ve read on this forum that hammering down a bulge actually hardens the metal. Is the entire bulged area now competent since it is hardened after being hammered down? What about being more brittle since being hardened? Are theire faults in the hammered areas that would be prone to rupture or is the area now sound and 100% competent? How would one know for sure after repairing a bulge in a high pressure area if the repair is sound or prone to rupture? I�m guessing electron microscopy looking for voids would be about the only way to tell for sure, but I�m not a metallurgist. I�d be interested in educated opinions. I have a friend who has a gun with this very problem, a ring bulge close to the forcing cone.

Bro. Buzz: I only play a metallurgist on the internet, but have been told by several smiths that ANY defect near the chamber/forcing cones makes the barrels unusable and unrepairable.

Then again

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.

The Clark had a bulge close to the chamber. It was worked down and passed proof. Then failed after six shells. So I would not even try to repair any barrel with a bulge within the first 18". Eyes and fingers are in that area and don't respond well to barrel failures.

You have studied metallurgy in Damascus, for sure there Drew. I�ve seen the electron micrographs to prove it. I�ve had gunsmiths tell me �no go� too and others who have said they possibly can make the repair. It�s very confusing and there is really no literature regarding what may be repairable and what isn�t. It�s sort of an alchemy sort of thing. The Clarke gun failed, even after British proof, but that�s no guarantee all will fail nor even a majority. I think it may well depend on multiple parameters including how bad the bulge is, quality of the metal material, thickness of the walls at the bulge, as well as others. The Clarke was a very old gun so the steel may have been archaic and not as good as more modern steels, but that�s only a guess. It would be nice if we had some sort of cookbook to go by defining what likely could be repaired and what can�t. There�s nothing out there defining that which I can find.

If the barrels were something like Siemens-Martin steel, Buturlin cited studies conducted at TOZ (Tula Arms Plant) listing Russian Siemens-Martin tensile strength as 85,300 � 92,400 psi; modern AISI 1040 gun barrel steel is 95,000-100,000.

I believe the concern on the part of gunsmiths is liability should something like this happen



Asymmetric obstructional 'ring bulge' related to the addition thickness of the brazed barrel flats and support of the right barrel



For a right hander, that chunk of chamber would go right past the left eye

And neither magnetic particle imaging nor radiography could show microscopic voids in the repaired bulge barrel wall

Obstructional burst just past the forcing cone.



The chunk hit the shooters forearm, but he only required sutures for repair





You might ask your friend to take a look

Not shooting guns with thin barrels, ring bulges, etc. is called risk management. Why anyone would is beyond me. Shooter beware.

popular wisdom says not to shoot guns with bulged barrels and not to attempt to repair barrels with bulges...

From what I�ve read all bulges are not the same. For example, it is perfectly safe to shoot many guns with bulged barrels IF the bulge is in a low pressure area, such as close to the muzzle. I agree, you are rolling the dice shooting guns with a bulge close to the breech and in high pressure areas. That�s the issue here, trying to define and identify those situations where a gun with a bulge near the breech may be safe from those that are not and which ones could be repaired. Or, should ALL guns with bulges close to the breech now render a shotgun barrel junk and then off to the junk pile?

There is no inherent difference in a dent and a bulge, except for the extent of it. One is pushed in, the other out. Metal is stretched in both instances. I have repaired both. Dents are much easier, because they're usually much smaller than ring bulges. There is much greater chance for a split to be present with a ring bulge, IMO. I cannot explain what actually occurs when you peen a dent out with repetitive light hammer pecks, not being an engineer or well versed in metallurgy, but it appears the metal "flows" back into nearly the original dimensional state. The only bulge I ever removed was a ring bulge that was about 10" from the muzzle on the right barrel of a 30" set. I knew I couldn't get it all, because it extended all the way around and was, obviously, under the ribs as well. After several sessions of peening, the top rib popped loose. This necessitated the complete removal of top and bottom ribs, and facilitated a more complete removal of the rest of the bulge. However, it was then found to have a split in the section of the bulge between the barrels, which was tig welded.

Bulges are bad news and, IMO, must be evaluated individually. The bulge I removed was what I would call a severe ring bulge, with much metal displacement ............thus, the split. I would never consider shooting, or repairing, one anywhere near the breech, and it would have to be a very "mild" one even then.

SRH