doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com what should be the minimum wall thickness of 12

bbob: do us all a favor and leave ole joe be.

Just noting: passing proof does not mean the barrels won't fail on firing, and unpredictably. To bring an example to mind, recall that Tony "Ballistix999" had that beautiful 20 ga he restored and it passed proof, only to blow out the right barrel on the 6th round he fired through it. Right near his foreend hand, too.

Have a read of this it may help.
http://parkerguns.org/pages/faq/BarrelThickness.htm

,Thanks Salopian. My family had an old damascus double that was that I killed my first deer with buck shot that I am sure was a mag load and we dove hunted with it for years with super X 2 3/4 dram loads. Just didn't know any better.

Some general observations made on the PGCA forum - Regarding accepted barrel wall thickness for shooting modern loads, it seems everybody has an opinion. Many of the gunsmiths that render opinions on wall thickness of 25 thou or above work more on modern guns than vintage doubles. If you ask a person who has spent his life working on fine VINTAGE double shotguns, they better understand how these guns were made and have much different opinions on the subject. Most all agree that even 18 thou in the forward half of the barrels is not dangerous from a bursting or bulging stand point, but rather the risk of dents and damage that cannot be repaired as there is not enough metal to work with. More on 18 thou later.

If you ask me, the Brits have been the fussiest about barrels for almost 2centuries, and set the mark for proof testing. Forget opinions based upon everybody bloviating and regurgitating what they have heard or what their friend's opinion is. The British proof houses regularly try and blow up perfectly good guns! They see what barrels can handle by passing not one, but two definitive proof loads through each barrel. I believe the loads are 18,500psi. We all shoot loads that are below 12,500psi (magnum loads), and most of us shoot more reasonable loads that run under 10,000psi. And the guys that have patterned their guns with loads like RST Shells recognize it is not speed that kills, but the nice even patterns premium ammunition provide. RST Shells don't exceed 8000psi. Go to www.rstshells.com for very affordable, safe loads for your beloved doubles.

If barrels with 20 thou wall thickness were regularly failing the proof they would not mention that as the recommended minimum. The facts are that barrels under 20 thou regularly pass proof and are deemed safe. Barrels with 20 thou and all other characteristicds in good shape pass proof in overwhelmingly high numbers. It is extremely rare for failure in the rigid proof testing for barrels in excellent condition because of wall thickness of 18 thou or above. Barrels fail for other reasons, but not often from bursting or changing bore diameters as in bulges. AND REMEMBER, THIS IS WITH 18,500 PSI LOADS!

Rob, is your gun marked "Not for Ball"? That mark came in with changes made in 1875, so yours might or might not fall into that category. However, if it's one of those, then it should have a mark for the bore followed by a B, like 12B, and another for the muzzle, like 14M. From the measurements you provide, it does sound like a honed out 14, but it's somewhat odd that it's a 12 that started life that far underbored. But if your bore and choke measurements are correct, it couldn't have been 14 at the muzzle because it's way larger than the 14 standard now. Interesting.

Jeweler, those heavy proof loads you mention would only be used if the owner or maker is requesting magnum proof (now called superior, and marked SUP under 2 crowns) on the gun in question. Standard proof (now marked STD with one crown), which is the old 850 bar proof, is about 14,000 psi--and that's the proof to which most vintage British game guns would be subjected.