doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Superposed ring bulges

This may be the dumbest of novice question but ..... could the bulges be repaired by cutting them out and reattaching the original barrels as if it were being slaved. Can't be to much taper, if any at that end?

Al

I examined a high grade Browning Superposed with a ring bulge in the lower barrel a couple of weeks ago. The only way you could tell there was a bulge was to run your fingers up the barrel. The bulge was about midway and the owner had no idea when it had happened. The rib wasn't displaced at all.
Jim

If not, it sure is way ahead of whatever is second dumbest. Seriously Al, two inches ahead of the forcing cone would likeely have a lot of taper, in addition to the whole idea being pretty silly. Since you asked.

Thanks Jim ...... I hate to come in second

Al

The inserts that terc is speaking of were called 'Super Tubes' by Browning and they were a PITA to clean up after .. and many didn't.

Bulges not a big deal; like any other repair, get it to a guy who's done it before an knows what he's doing. Nowadays stripping and relaying ribs on S/Ps seems to be routine when reducing bulges or peening out dents. Provided the side ribs aren't damaged or distorted, many times an experienced smith will not remove them. Rebluing is just about mandatory after peening the barrels, but the result is more than pleasing aesthetically providid the gun is not a "white" gun to begin with. KBM

Plastic deformation occurs when one has exceeded the Yield Stregnth of the Material. Below that Stress the material will return to its original shape after the Stress is removed. Plastic deformation also introduces dislocations or disruptions in the lattice pattern that does cause the material to resist elastic deformtion or 'harden' i.e it becomes brittle like the wire example given but and this is the big but, the lack of elastic deformation means that the material is subject to brittle failure where a low stress can cause the material to fail catastrophically! Obviously one wants to stay in the elastic deformation region for steel in gun barrels and once the material has entered the platic deformation region, catastrophic failure can occur at a stress lower than the normal stress from firing a factory load.-Dick

A barrel bulge is cause for concern and appropriate investigation, but it is not necessarily catistrophic for the barrel. Just as not all skids result in a car crash, still we avoid skids to the extent practical.

Note that words like "soft," "hard," "elastic," and "brittle" are qualitative and not quantative. Steel is not either soft or hard or elastic or brittle. It is some quantative combination of these qualities.

Lets carry the metalurgy a bit further. Stress is the amount of force applied to a piece of steel. Strain is the amount the steel deflects/moves in reaction to stress and stress level is the reaction to a specific amount of strain. Common logic says that a piece of hard steel will have less strain for a given stress level than will a piece of soft steel. In this case, common logic is basically wrong. The hard steel will strain to a greater extent without plastic deformation than will the soft steel; this is why springs are of hard steel. To the point where the soft steel yields, the stress-strain relationship is basically equal between a hard and a soft piece of steel.

In the case of the bulged barrels, it will take a higher stress to increase the bulge (to increase the amount of plastic deformation). The bulge will not grow from normal firing if it is not cracked. Steel work hardens due to strain. In the example of the wire being bent, the strain is fixed by the amount of bending, not by a given stress level.

An overly hard steel may act brittle. That is, it will break at low strain levels. However, this is due to crack initiation at a stress riser, such as a scratch in the surface. As I recall, Browning super barrels are relatively soft. Therefore, I'd expect a wad 'o tabakky lookin' bulge before the bulge cracked. Also, being soft, they are much easier to work down the bulge.

B - not a dumb question, but, obviously, you aren't visualizing the sleeving process as it happens. Note that the sleeve extends full length of the barrel. So, if you did have enough metal to allow rechambering the barrel on the muzzle side of the cut, you would wind up with some mighty short barrels. Say the bulge is 4" in front of the back of the chamber and you had to cut out an inch to eliminate the bulge. You need enough "meat" in the barrel tube starting at the cut to allow chambering. And, you loose 5" of barrel length as you set the barrels back to the chamber face.

Bouvier,
As Rocketman said, cutting out the bulge is not practical. However, this kind of damage could be repaired a couple ways.

One way would be to sleeve the barrels. This would involve cutting the barrels off a about 3 inches from the breachface and boring out the chambers to a larger diameter. New barrel tubes would be turned down on the back area to match the bored out chambers. The tubes would be soldered in and the outsides blended to the original barrel section. Ribs would be reattached and the barrels blued.

Another way would be to work the bulges down with hammering while a mandrel is in the bore. If the bulge is in the forcing cone, this could make it more difficult to cold forge the barrels down correctly.

Browning "Supertubes" are about 16" long. I don't think they would be the culprit in a bulge where these occurred.