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

A local shop has a 1970 12 ga. Superposed in for cleaning. Both barrels, upper more so than the lower, have a ring bulge about 2 " in front of the forcing cone. These are old bulges. Gun has been shot regurarley for skeet since the damage. The current owner does not know how the event occured that caused the bulges.

Question is: Exactly what sort of safety danger do theses bulges represent in this location. My opinion is it is a danger only for another pressure spike event.

What say you all!

The plastic deformation of steel (yielding) strengthens it. It is unlikely that the bulge would grow from normal use. Note the breaking of a wire by bending back and fourth. The bend wants to move away from the original location as the OL becomes stronger than adjacent material; you have to force the wire to bend in the same place to get it to break from strain beyond its ultimate tensil strength. The bulges were likely caused from a bore obstruction.

Unsightly - yes. Dangerous - not likely.

Can these be fixed so as not to be visible?

The good news is that with the bulges located 2" in front of the forcing cones, at least you know where the catastrophic burst will occur next time there is a barrel obstruction. You can situate your fingers accordingly when you are shooting.

You should think about this especially when you're shooting clays for money...Geo

Sometimes bulges and dents can be worked back into more or less original size and place. But, it will not be cheap.

GN - an obstruction bulge will occur at the obstruction. The gas hammer over pressure is a localized phenom.

Rocket, you're right of course, and I was mostly just kiddin', but I'm not sure I agree that its good advice to ignore bulges or to infer that bulges just make the barrel walls stronger...Geo

Geo,
I think Rocketman is qualified to make that inference. But you're right, a bulge should be at least inspected to be sure it's free of cracking before a gun is fired again.

Sherman Bell's current "Finding Out for Myself" article in DGJ may indicate there's more cause for concern with a bulge. Of course he was shooting proof loads in barrels the walls of which had been thinned considerably by honing, but the first gun he succeeded in destroying first established a noticeable bulge in one barrel, then burst at the spot of the bulge when the next round was fired.

Bit surprised it didn't pop the vent rib or side ribs.

jack

docbill, A possible explanation. I've been told it was common among skeet shooters to use chamber inserts in there guns.The inserts ended just beyond the forceing cones.If the gun wasn't cleaned properly carbon rings would form in the barrels were the insert ended. The carbon rings acted as an obstructions causeing bulges directly behind the rings.Browning actually made these inserts for Browning guns making the bulges more common in Brownings than in other guns.
Dave