doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Thin barrels passing London proof

There is no such thing as minimum wall thickness to pass proof and there never has been. Ever.
They either pass proof or not. Wall thickness is immaterial and not even measured.

Thanks very much for all the good comments. Much appreciated.

popular wisdom suggests that one should not shoot a fluid steel barreled gun with a barrel wall thickness of less than .030 inches...so why take the risk, of shooting a damascus barreled gun with such thin barrels? makes no sense to me...when there are plenty of fine heavier barreled damascus guns that are safe and fun shooters with black powder loads?

�Popular wisdom� what is your reputable source for this fact?

While some may throw out a number, it is a throw not necessarily a fact based on testing. This why there is a proof house to provide some reliable basis for judgement.

While 0.025 is on the low end, as others have already noted it depends on where. My father and I have put more than a thousand shells (custom low pressure sub 6k) through a pair of Damascus barrels barrels which are below 0.030.

Blue Grouse is totally correct: MWT's have never figured in the proof test. The Proof House RECOMMENDED a MWT of 20 thou until steel loads became common and has now increased it to closer to 30 thou.
Ed Good: there are relatively few damascus barrels out there that measure in excess of 0.025" MWT's. They may have started life with nice thick walls but old corrosive primers, rebrowning etc have reduced most to high 20's at best, many are in the low 20's.
Karl Graebner: when measuring MWT's, you slide the barrel up and down the gauge looking for the minimum reading, whether it is just in front of the choke or just in front of the chamber.
I exaggerate because it is very difficult with a traditional MWT gauge to measure up close to the muzzle and most MWT gauges are about 15" long so unless one suspects something scary, one stops at that point from the muzzle.
There is no particular place that one states the MWT for, it is any spot on the barrel. If it was in a 'bad' place then I would state that in describing the gun.
As a point of interest, most barrels made in the UK from the last 1/4 of C19th to present do not taper from muzzle to breach.
They are often described at 'Eiffel Tower' profile, ie. they taper to around the mid point then the MWT's get slightly greater toward the muzzle. I understand that gives better dynamics to the barrel, reducing overall weight but increasing the strength of the tube near its end to accommodate the choke and risk of impact damage.
This means that if the bores are properly parallel (often not the case with guns that have been 'creatively' bored [!]) the thinnest MWT's measurement will be in the mid section of the barrels. On post 1880 guns, I find this is usually the case.

Toby,
Great explaination, thank you for posting. Having purchased my first English double after owning several other SxS's had led to my curiosity.
Karl

I believe it would be unwise to purchase a vintage double, of any maker, without knowing, or being able to measure accurately oneself the end of chamber, forcing cone, 9� from breech, 9� from muzzle, and exactly where the MWT is found.
And breech to muzzle bore measurement looking for a bulge not apparent on external examination.
Bad things happen to good guns after 100 years or so.
https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/edit

Bro. Toby's "Eiffel Tower" profile is well said and fits my experience with U.S. makers also

Standard dimensions of each barrel tested as part of the 1891 Birmingham Proof House Report from "The Field" March 7, 1891 Vol 77:325
http://books.google.com/books?id=inQCAAAAYAAJ&pg=PA9
NOTE: these dimensions do NOT represent MWT, but show the "Eiffel Tower" profile. The chambers are not cut nor do the barrels have choke constriction



Mark Twain
�It is better to be careful 100 times than to get killed (or kill a bystander with a chunk of shrapnel) once.�

"Experts on Guns and Shooting", George Teasdale Teasdale-Buckell, 1900
http://books.google.com/books?id=4xRmHkr7Lp8C&pg=PA526&source

My personal policy is MWT has to at or north of .030. That eliminates some nice guns from my consideration, but my fingers appreciate knowing the barrels have extra meat in them. Again, just my personal policy.

I had an untouched Damascus CH Parker 16 and Crossed Chisels measured it at .018 and .022. Both thin spots were about 6 inches from the barrel ends. The barrels had not been honed, they were just struck that thin. Far as I know it is still knocking birds down with the appropriate ammo.