doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com The Value of Proof

Yes we do. It's 'at least' 130% of mean service pressure.

I think this all suffers in translation from the English.

Blackpowder Pressures from Sporting Guns and Gunpowders: Comprising a Selection from Reports of Experiments, and Other Articles Published in the "Field" Newspaper, Relative to Firearms and Explosives, Volumes 1-2, 1897



Definitive proof was 6 1/2 Drams Proof House Powder with 1 2/3 oz. No. 6 shot = 4 1/2 Long Tons LUP or about 14,000 psi.
6" Proof Pressure was not reported but looks to be about equal to 72 gr. C&H No. 2 T.S. (somewhat similar to FFFg) = 3.2 Tons = 9,632 psi

So what is the Mean Service Pressure suppose to be at 6 3/8"? CIP doesn't list a target number.

That's the chart I was referencing, Drew.

I eyeballed the 9" point which is where this all started and guesstimated 2 tons.

That's a whopper of a proof load, and if the pressure curve is anywhere near correct the strength of blackpowder proved guns has been underestimated for generations.

Perhaps this is the chart that gave rise to the idea that black maintains higher pressures down barrel longer than smokeless.

"So what is the Mean Service Pressure suppose to be at 6 3/8"? CIP doesn't list a target number."

'The Masters' are apparently able and authorized to measure that in their pressure guns from representative cartridges and then load their proof rounds accordingly.

It's not important that we know, only that they know.

Hey! Maybe that's the root of the proof failure epidemic.

Suppose CIP cartridges have gotten hotter and proof loads have followed?

I know that sounds blazingly stupid since the cartridges are supposedly tested, but do they test at 162mm? If so, why no data as Drew points out?

A not so bad guess would be that CIP cartridges are probably lower pressure than their rating to try to keep the liability hounds at heel. And, the standard greeting is, Hi, I'm from the proof house and I'm here to help.

Very interesting. We've discussed the 1929 Hunter Arms Proof Load Pressure Curve Chart in the past
http://library.centerofthewest.org/cdm/singleitem/collection/WRAC/id/8149/rec/107

12g 2 3/4� was proved with 6.5 Drams FFFg with 1.687 oz. shot = 14,200 psi at 1"
Pressure was about 9,500 psi at 6"
Pressures were measured by crushers (LUP - Lead Units Pressure) and modern piezoelectric transducer measurements would by 10 � 14% higher

Well, CIP maximum is generally lower than SAAMI maximum so to get any decent performance CIP shells appear to need to be loaded closer to maximum peak under their standard.

The total work done by a shotshell is represented by the area under the pressure curve, so a lower peak pressure MUST be offset by some additional pressure down barrel someplace.

Charts 'proving' that this is 'not much' have been posted, but the fact remains that to get to 1200 fps for example, any shell loaded under any standard has to do the same work.

Being European modern re-proof means I'm willing to pay extra for ole' grand daddy gun so tested. Able to shoot modern ammo of appropriate pressure is big plus. In America people collect guns and sometimes shoot them knowing that "Model T can't be driven at 80mph w/o engine blowing long before that speed is attained". Americans have RST and Polywad catering to people shooting antiques w/o modern re-proof. When recommending light weight game gun on European forums the likely candidates are vertical guns from Beretta, B.C. Miroku and if looks are acceptable Merkel Bros. it is almost never something real old with short chambers or twist or damascus barrels. The gold standard for SxS classic is Webley & Scott 700 series from Birmingham sadly discontinued many years ago. There are suitable copies from Germany, Italy, Austria, France, Spain,..... Limited new SxS game guns means Fabrique en Turkye. Different worlds different beliefs and customs.

Toby, a question for you.....: I'm assuming the barrels on your Blanch survived the proof testing with only the action failing. If you fit these barrels to another action will they then have to go through proof AGAIN to be legal? Also, I'm sorry for the loss of the action. Having a love for antiques as I do, it almost makes me teary eyed to look at the Blanch action photo.