doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Possible Barrel Repair

Some time ago I noted that my Franz Sodia 12 bore o/u had been shown to have a spot a mere 6 thou thick in the top barrel. The barrels are Bohler super blitz steel and the gun was in regular, but not hard use for almost 30 years with no problems. Last week, the gun went with me when I picked up my Charlin that gunsmith Gunter Pfrommer has put back in superb shape. He looked at the Franz Sodia, measured, and confirmed a thin area on the left side of the top barrel about 12 inches from the breech. That thin area is 6 thou (.1524 mm).

Some months ago I tried to get the Slovenian gunsmith that Montenegrin recommended to quote on making a new set of barrels. He eventually replied that he could not source barrel tubes (!?). I've just emailed him again.

Of interest is that Gunter speculated that the thin area resulted from a mistake by a workman filing to clean up after laying the ventilated rib. His file slipped, marring the side wall, and he likely smoothed the scratched area out resulting in a too thin section. The gun passed proof.

The question for more knowledgeable Board members is whether that thin section of the barrel wall might be marked out and then tig welded to be ultimately filed down to an acceptable wall thickness and reblued. If that is possible and sensible, who might do it?

Best of the Season, Tim

It hasn’t failed in 30years use, and if it did would not be near your fingers.

IF you could successfully weld on an outer layer how can you know it will be any stronger.

Briley 20 bore inserts?

Tim- I've done a fair amount of code TIG welding on piping systems, mainly in power plants. The main concern in welding any circular section is controlling the HAZ- heat affected zone. The first rule in TIG welding is (1) Know your parent metal. You want to build up, and then later, file back the built up area to match the circumference of that affect barrel on your Bockflinten--shame that someone made that mistake years ago, but as another member suggested, if it hasn't failed over time (so far) perhaps staying with light loads might be the best way to go.. RWTF

I'm not a welder by trade, but have managed to do some fairly intricate TIG welding on thin materials. However, I would not even dream to attempt what you are proposing, and don't know of anyone who could do this with any guarantee of success. Laser welding is another process used for intricate repairs on thin materials. But while it is often used to fill and repair small pits or cracks, I have not seen it used to build up a relatively large area.

First off, at only .006" of wall thickness, the area you wish to build up with TIG weld is only slightly thicker than a piece of standard printer paper, which averages .004"- .0045". So you would have to be capable of welding paper thin steel without burning through. At minimum, a close fitting copper plug would have to be made to avoid any build-up of dingle berries in the bore. You would also have to fill the bore with inert gas or take some other precautions to prevent scale formation. You would presumably also have to do this over a relatively large area in order to subsequently strike the repaired area, in order to blend it in to the surrounding areas that have what is considered normal and adequate wall thickness.

Then there is the question of HAZ (Heat Affected Zone), as mentioned by RWTF. It would be difficult to know the effect upon the metallurgy of the repaired area without costly testing. And temperatures high enough to anneal or stress relieve would certainly be higher than rib soldering could withstand.

I am curious how you or Gunter Prommfer could be certain that this gun passed proof after the barrel was struck this thin? If it did, that's pretty amazing, and illustrates why the frequent posting of Burrow's bursting formula on this forum has no bearing on barrel wall strength. A closed steel tube .006" thick at normal pressures found 12" from the breech would pop like a child's balloon. I've seen enough hydro-testing failures of much thicker tubes to be confident of that statement. It is interesting that it hasn't bulged or blown just using standard loads.

If I was in your shoes, I'd be setting this gun aside and start hunting for a set of orphan barrels that could be fitted. But having once experienced about a half hour of total blindness from getting hit in the face with powder gasses, maybe I'm just being unreasonably cautious about these scenarios. However, I can promise you... a lot of shit goes through your mind when you suddenly lose your eyesight.

Sleeving with the joint tig welded is one way to go and it is a bit easier and much more successful then what the op suggested

Is this the one Briley sent me for a sleeving quote? It’s a difficult sleeving job, the two piece forend, the OD where the seam would be was to minimum for 12ga, I actually recall to do the job I required stepping down to 16. It was an expensive one.

No way in hell I’d attempt TIG welding or laser welding.

I think Keith nailed it.

As another code welder I'll second what Fox and Keith stated. That is twice the thickness of a human hair. It probably didn't burst because it is a small area kind of like a corrosion pit.

Yes, gunmaker, it is the very same o/u 12 bore that Briley asked you to sleeve. Haven't so far had a quote I liked for making new barrels so wondered as above that some sensible fellow members have shot down. Thanks lads. I'll keep looking for new barrels.

Regards, Tim

Words of wisdom, indeed Sir.. RWTF