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

Actually, if it's an 1880 gun, the "fractional" bore sizes--which give you a much better idea of the gun's early bore diameter (12/1, 13/1 etc) than does just "12 gauge"--were not yet in use. Although the standard bore diameter for a 12 gauge in 1880 was .729, just like it is now, the next larger bore (an 11) had a standard measurement of .751. Therefore, a 12ga gun made in 1880 and not reproofed since then could have had a bore diameter a good bit larger than .729 when it came from the maker and passed proof.

without spliting hairs, or telling you what you want hear, find a qualified smith with the proper tools and have him inspect the gun...if he finds barrel wall thickness less than .030 in the upper half of the barrel, then do not shoot the gun. it aint worth the risk.

My gun passed proof not too many years ago in London at 25 thou. I don't worry about it at all.

The general opinion is that barrels should have at least .025" MWT but this has nothing to do with "proof". Many English guns with less than .020" MWT pass proof both with fluid steel and damascus barrels.
A great number of English guns did not even have .030" MWT when they first left the factory but all had to pass proof.
I have a Greener with Siemens fluid steel barrels with .020" MWT and they passed re-proof. Would they stand a dent removal? Probably not, which is why the recommended .025" MWT for better durability and longevity.

It's a 1880 gun bores are .737 and .733 bore with .025 thickness at 9 inches he is shipping it to me to check out.I am not sure when it was proofed last.I am only going to shoot black powder probably with it which I am real comfortable with the results.

NO pits by the way or rust,

9" from the breech or 9" from the muzzle.

9" from the breech I ain't shooting it.

9" from the muzzle and I'll run RST's and my low-pressure reloads through it all day long if it's otherwise a solid gun.

I have a J&W Tolley that went through Birmingham proof in 1989 at a wall thickness of .024 - near the muzzle.

I understand it's .025 9 inches from the breech that is important.
I thought black powder is a lot lower than a RTS low pressure but I am only guessing.
maybe I misunderstood something.

Drew thanks for the info seems very imformative.

Sounds awful. It should be .045-.050" 9" from the breech. I think more than .010" have been worn away at that 9" mark, perhaps more.

Somebody here had an English gun that passed re-proof at .018, nine inches from the breech. Can't remember the level of proof, may very well have been black powder. It raised eyebrows, however. With the new two proof load firing in each barrel that is causing trouble these days, it likely wouldn't pass today.
They might pass proof, but, they will also dent pretty easily.

Best,
Ted