English Best wall Thickness
 

Hi,

I am looking at a best gun in 16bore with min wall thickness of .18 and .19

Would this be in immediate need of being sleeved?

John: to provide any sort of advice, we/you need the wall thickness measurements at the end of the chambers, the forcing cones, and every inch out to the muzzle; esp. 9" from breech and 9" from muzzle.
The location of that thin segment is critical.
Are the barrels fluid steel or pattern welded?
Has it been proved with that MWT?

We have to know the wall thickness at various places. Your mentioned wall thicknesses at areas close to the breech are unacceptable, but more acceptable very close to the muzzles.

While only for curiosity sake, it would also be nice to know the maker of your potential "Best" gun. But the really critical stuff involves those wall thickness measurements and where they are located. UK Gun trade minimum wall thickness is .020. Purdey's won't accept anything under .022.

If that gun is not in proof you will suffer from a costly event. Take it to a qualified gunsmith to determine if it is in proof. If in proof, you have to determine if you want a gun with thin barrels.

In this case it probably doesn't matter where these measurements are. That is very thin regardless of where the measurement is. And remember, the smaller the gauge gets, the higher the pressure goes.

Granted 16 gauge pressures are not too far off from a 12, but if the bare minimum for a 12 ga. is .020, that should tell you something. If this is a best gun (and everything that implies financially), it could not be submitted for proof with those measurements. If the sleeving is done here in the US, and not re-proofed, it does significantly hurt it's re-sale value down the road. May or may not be a consideration right now, but is something to think about before a price is agreed upon.

Take a look at a .018 or .020 feeler gauge . I did. I don't think I would be comfortable with it.
Dave

Forrest: The Birmingham Proof House does not reject barrels for proving based on wall thickness, and if that .018" is out toward the muzzle, it could well pass.
http://www.gunproof.com/Proofing/proofing.html
The barrels are at much higher risk of a dent.

While we're here, some factory small gauge Parkers have been documented to have MWT in the distal barrels less than .020".
http://parkerguns.org/pages/faq/BarrelThickness.htm

In simplest terms the current owner of this gun is trying to make his problem your problem.

That depends on how you define "problem." And the price of the gun.

Let's see...

A well-priced Purdey with barrels .018 out at the muzzles?

Or a mainstream Parker VH with plenty of thickness throughout?

Personally, I'd take the Purdey in a heartbeat. Then be careful about dents.

But this is all banter. "Gunner" must make the choice.

Thank you, I stand corrected. I always thought that the proof houses had a minimum standard of what they would accept as far as wall thickness. I confused that with what the gun trade informally holds as a minimum standard.

The U.S. has no proof house, as opposed to the U.K.

Caveat Emptor

John is correct, which is not to say the guns were not proved.

Parker Brothers 1893 Catalogue
“Our guns are bored on the latest improved system for shooting Nitros, or Smokeless Powder, and all our guns are tested with some one of the most approved makes, and a tag accompanies each gun, giving the results of such a (pattern) test.”
(No records exist regarding the specific proof load in that time period.)

“A Trip Thru Parker Bros.”, 1923. Courtesy of Jeff Kuss

http://pic20.picturetrail.com:80/VOL.../412230865.jpg
http://pic20.picturetrail.com:80/VOL.../412230864.jpg

A Parker Service and Proof Load table was published in the 1930s and reproduced in the The Parker Story p. 515. 12g 2 3/4” shell Service Pressure is 10,500 psi. Definitive proof used 7.53 Drams (no doubt) black powder and 2 oz. shot with a pressure of 15,900 psi. The pressure was measured using LUP and modern transducer values would be 10-14% higher, or more than 17,500 psi.

LTC Calvin Goddard writing in “Army Ordnance” in 1934, reported that Parker followed the SAAMI standards then in force: 13,700 psi proof, 9500 psi service for 2 5/8" chamber; 15,900 psi proof, 10,500 psi service for 2 3/4" chamber (by LUP) + 10-14% for modern transducer measurement.

Interesting article. Two questions come to mind.

1. If the barrels are not properly regulated upon POI testing how did they change the regulation on a finished set of barrels?
2. The article states that after proof each barrel is stamped on the flats. What does that mark look like?

Here's an example on a late Remington Parker but that "OVERLOAD PROVED" stamp was used on Parkers in the later Meriden days.


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Looks like the article Drew provided above is dated 1923.

It is well to keep in mind that the "proof safety" of any gun barrel is only valid at the factory, and for as long as the subject barrel remains unaltered.

Within the decades that many of double guns we admire have existed, they have stood liable to a panoply of factors that can negate proof. Parker, British, or otherwise. Most of these factors involve a host of bodgers who may have attacked the barrel with various implements over the years. To shorten, open, hone, lengthen chambers or otherwise alter the barrel to a less than safe condition. Especially with the use of certain ammunition.

Thus, most if not all classic doubles should be assessed by a professional and competent double gunsmith before any verdict is rendered as to their safety and suitability for shooting today.