Proof Marks on a Greener - Interpretation?

[Jack Cronkhite]

Hi: "itis" is a terrible disease. It can mutate and who knows where that can lead. Saw this little gun and it is pretty. What can be understood from the proof marks? Continuing education.

Thanks,
Jack

[charlie cleveland]

i really like the 7 /8 choke marks..does this mean a tight modified or a lose full.....very interesting...charlie

[Jack Cronkhite]

Okay, with the Greener is a Churchill (yes there were also some Parkers). Now these marks tell me more than on the Greener. 3 1/4 Tons/square inch, if I have that right, means a pressure of 6500 psi. Yes???

Does BNP infer 3 1/4 Tons, and is that why the Greener doesn't state a pressure?? Lots to learn still.

Thanks,
Jack

[Mark Ouellette]

Jack,

Those are Long Tons by the lead crusher pressure test. PSI ratings are by piezo-electric method. The two methods are not a apples to apples conversion...

The following is from a thread on doublegunbbs.com:

PROOF/PRESSURE

British proof markings: The "tons" mark (which is service pressure) was not used until 1954.
- Between 1925-54, the chamber length was marked. 1904-1925 guns would not have the chamber length, but only the shot charge and a nitro proof. http://www.gunproof.com/Proofing/proofing.html

Information about the Birmingham Proof House
http://www.basc.org.uk/media/100_proof.pdf

There are three pressure measurement systems (lead crushers/LUP, copper crushers, and piezo), and two standard systems of measure units (USA/SAAMI and CIP/British/European) and two differing units (psi and tons and bar and Kg/Cm sq) within each system, different proof laws by country, and differing proof laws by age.

Unfortunately, there is essential NO formula to convert BAR expressed as LUP (CIP) to PSI (SAAMI). LUP + 1000 does not reliably predict the actual piezoelectric transducer measured pressure.

In 1989, all proof data was marked in metric using the BAR as the unit of measurement. The use of TONS per sq. inch was dropped. Under this system, 850 bar represented standard proof, with 1200 bar being special or magnum. 2 1/2" chambered guns are usually proofed 850 bar

2 3/4" chambered may be proofed 900 bar (3 1/4 tons per sq. inch) or higher.

**650 bars is standard CIP (British and European) service pressure for shells designed for guns proofed at the CIP standard of 850 bars**

European (CIP) proof pressure of 850 kg per sq. cm. (BAR) = 13,920 psi proof pressure= 10,730 psi service pressure (SAAMI)

Per the 1954 Rules of Proof, here are the equivalent service pressure values:
- 3 tons--8,938 psi
- 3 1/4 tons--9,682 psi
- 3 1/2 tons--10,427 psi
- 4 tons--11,917 psi

These numbers SHOULD apply to guns proved under the 1925 rules, which were stamped only with chamber length and shot charge. Thus, a 2 1/2" chambered gun, 1925 rules of proof, would be equivalent to 3 tons; a 2 3/4" chambered gun to 3 1/4 tons.

A service pressure of 3 tons per sq. in. = 8,938 psi service pressure (SAAMI)

For comparison, here's data from actual pressure testing:
- 3 Dr.Eq. 1 1/8 oz. Winchester Trap Load 1,202 fps 9,600 psi
- Winchester AA Xtra-Lite 1 oz WAAL12
1189 fps 8000 psi

Standard 1900s loads per LC Smith Hang Tags:
12g 3 dram 1 1/4 oz 1165 fps
16g 2 1/2 dram 1 oz 1165 fps
20g 2 1/4 dram 7/8 oz 1155 fps

The 12g 2 5/8" 1 1/8 oz. 3 1/4 Dram Eq (1295 fps) load of the 1920s ran about 10,500 psi.

The Super-X 2 3/4 inch 3 3/4 dram equiv. 1 1/4 ounce load (1330 fps) was near the SAAMI max. of 11,500 psi.

[Jack Cronkhite]

Thanks Mark. There's a bit of reading here to understand. Forgot about long tons. The psi sounds a lot better now.

Cheers,
Jack

[Jim Akins]

Jack the 1977 Gun Digest has a good article on British proof marks and history of Proof in England, interesting reading. If you cannot find a copy, email me and I can scan it for you.

Jim A.

[lee r moege]

Jack: IMHO the 20 bore is an earlier gun than the 12 and the 7/8 is what shot charge size it was proofed with. It is nitro proved of course and the markings "choke" just means it has some. The chamber length is probably 2 1/2" and you would have to measure the barrels to determine the chokes. The B proofs are , "provisional" and "final". If you don't have any luck in your search for info give me a PM and I will dig out my antique set of Burrard's books. They are the "last word" in Britsh guns at the turn of the century, and have all that neat suff packed in three volumes. Happy searching!. Lee.

[Frank Cronin]

Thanks for the great information Mark!

Frank