1 psi = .06895 bar
1 bar = 14.50377 psi


600 bar = 8,706 psi

650 bar = 9,432 psi

700 bar = 10,157 psi

800 bar = 11,608 psi

850 bar = 3 tons = 12,328 psi


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

Per Larry Brown: "Per the master of the Birmingham Proofhouse, the problem with any psi/BAR conversion is that BAR still means crusher BAR, not Piezo BAR, to the Brits. Proof pressure is 13,920 psi; service pressure 10,730 psi. This is very close to equivalent to American standards before modern, 2 3/4" shells were introduced in the 1920's."

Information about proof: http://www.basc.org.uk/media/100_proof.pdf

Conversion table

http://www.unitconversion.org/unit_converter/pressure-ex.html
http://www.bandpusa.com/files/db_trio.pdf




1 ounce = 0.0625 pound= 28.35 grams

24 gm=.85 oz.=just less than 7/8 oz.

28 gm=1 oz.

32 gm=1.13 oz.=1 1/8 oz.

34 gm=1.2 oz.=1 1/5 oz.

36 gm=1.27 oz.=just more than 1 1/4 oz.



SHOT SIZES


US UK Italian

mm inches mm inches mm inches

4 3.3 .13 2.8 .11 3.1 .122

5 3.0 .12 2.67 .105 2.9 .1145

6 2.8 .11 2.54 .10 2.7 .1065

7 2.54 .10 2.4 .095 2.5 .0925

8 2.3 .09 2.29 .09 2.3 .091



UK

http://www.kwacs.org.uk/barrels&choke.htm
http://www.hrwscothunt.ndtilda.co.uk/info/data.htm


From the Eley Shooter's Diary, 2005:

British 4 3.1mm, .12", 170/oz

5 2.8mm, .11", 220/oz

6 2.6mm, .10", 270/oz


Italian

http://www.bandpusa.com/files/productguide-USA-2005.pdf

Drew, this is still confusing to me. Are you saying that SERVICE pressure is 650 BAR for guns PROOFED at 850 BAR? Does that mean that any shells marked CIP will be no higher then 650 BAR which is 9,432 psi or can they be as high as the 10,730 psi Larry quoted?

Then to further complicate things on the back of those Eley shells we bought it says: "For use in guns with 2 1/2"/65mm or longer chambers marked for a service pressure of at least 3 tons per sq.in. or a European proof pressure of 850kg per sq.cm.and/or a shot load of 1 oz.."

Larry

850 bar = 3 tons = 12,328 psi

Is that correct, what's the PSI on 4 tons of proof after 1954 ?

Great read.
Thanks

DT: I was a bit apprehensive about posting this data and we talked it over quite a bit on 16ga.com. The back of my Eley Grand Prix loads say the same thing and Eley never responded to 2 requests for pressure data (please see this thread http://www.16ga.com/forum/viewtopic.php?t=2410 )
Larry understands this better than I do and had an article in Shooting Sportsman a couple of years ago about proof testing. Federal responded to my request for pressure infro regarding their 16g Game Shok 1 oz at 1165 fps and said only 'it runs between 9000 and 10,500 psi.' That has been the standard 16g 'Field' load for more than 80 yrs and I must assume it is acceptable in '3 ton' proved guns. You'll note though, from the above thread, that several makers have 1 oz loads running closer to 8000 psi.
You'll also note that the shot size data from Eley is different that TWO other websites. England and American-2 nations separated by a common language!

BTW: this pressure-speed chart from B&P helps understand the relationship between psi/bar http://www.bandpusa.com/files/db_trio.pdf

4 tons would equal 16,437 psi.

Larry

In the appendix to Burrard's "The Modern Shotgun" he reported on tests run in england in which a pressure gun was set up with a lead crusher on one side & a piezo electric tranducer on the other, thus recording both pressures simultaneously. An attempt was then made to work out a conversion value for the presures. It was found that for pressures within the normal range of shotguns this could be accomplished by the following formula. LP = crusher pressure & EP = piezo electric pressure;
(LP x 1.5) - .5 = EP. As the british use the "Long Ton" of 2240 lbs the tons can thus be converted to psi. This formula gives 8,960psi for a 3-ton "Crusher" pressure & 12,320 for a 4-ton crusher pressure. Where most confusion comes in is in correlating "Service Pressure" with "Proof Pressure". 12,320psi would be a proof pressure for a gun intended for a 3-ton (8960psi) service load while the 16,437 psi would be proof pressure for a gun intended for a 4-ton (12,320psi) service load. One of the Greener-Martini Police Guns I once had carried a 4-ton service proof. It would not have been intended to fire service loads of 16,437psi.

The Italian shell maker B & P sells a 2 3/4" shell marked 1050 BAR. If they are using the same standards that is over 15,000 PSI David

David, I have that same 1050 figure in my email from the Birmingham Proof House. That's "magnum" service pressure (measured with a transducer). And you've converted it correctly to psi. That's way higher than SAAMI service pressure on anything except a 3 1/2" 12ga.

David: the highest bar I find on the B&P chart linked above is 800 or 11,608 psi.

Drew, you should know better than to trust those sneaky Italians!:)

Birmingham Proof House says: "CIP crusher service pressure for High Performance (magnum) is 900 bar service, proof 1200 bar; the transducer values are 1050 bar service, 1370 bar proof."

Sometimes what you read on the shell boxes isn't correct. For example, on a box of Gamebore Pure Gold 65MM shells, it says that the shells can be used in guns "proofed to a service pressure of 3 tons per square inch (850 kg per square cm)." But we know that while 3 tons is a service pressure, 850 kg (bars) is in fact a proof pressure.

LB - The box is covering both bases; guns marked for 3 tons of service pressure (understood to mean that the proof load was 850 bar) and guns marked for 850 bar of proof pressure (understood to mean that the service pressure is 650 bar). We have two uses of pressure (service load and proof load), we have three measurement systems (lead crushers, copper crushers, and piezo), we have two standard systems of measure units (USA/English and SI) and two differing units (psi and tons and bar and Kg/Cm sq)within each system, differing proof laws by country, and differing proof laws by age. I think it is remarkable that we get it as clear as we do!!

If you are going to shoot 100+ year old guns, you will have to get past looking for the simplicity of simple conversions and understand what the proof markings mean.

It's clear enough to me, RM--but only because I know a bit about service pressure, proof pressure, etc. But I'm a writer and tend to be a stickler about clarity of language, and the language on that box is most definitely NOT clear as written. It gives the reader the impression that 850 bar is the service pressure of a gun marked 3 tons, which would mean that such a gun was built to accept standard SAAMI loads--which it most definitely was not.

Keep in mind, SAAMI cup, lup, & pizo, CIP lup cup & pizo, and the old British method are seven DIFFERENT ways of MEASURING the pressure and will yield seven different numbers, conversions aside. There is simply no way to directly convert from one to another, they have only a loose correlation.