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Forums10
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Apr 29th, 2024
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Joined: Jan 2002
Posts: 11,381 Likes: 106
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 11,381 Likes: 106 |
Drew, not sure where you got the tons conversion data you credited to me. But it's been a LONG time ago . . . but definitely not from my SSM article on proof.
Things are definitely clearer on this side of the pond since the establishment of SAAMI. On the other side . . . it'd be clearer if the Brits wouldn't have used metric values (bars) to express measurements taken with crushers. Sometimes I think they enjoy confusing their American cousins!
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Joined: Jan 2006
Posts: 9,428 Likes: 315
Sidelock
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Sidelock
Joined: Jan 2006
Posts: 9,428 Likes: 315 |
Here's your post in 2008 Larry. I couldn't go back on DoubleGun past the 2007 discussion but it all probably started before then http://uplandjournal.ipbhost.com/topic/6351-chamber-pressures/Digging through my files, I found the following information--which, although the pages in question do not indicate for sure, I believe came from the Birmingham Proof House. Here we go: 1954 Rules of Proof Service Pressures Converted to Approximate CIP values 12ga, 2 1/2", 3 tons: 6720 psi lead crusher system (LC), 8938 psi transducer (CIP) system 12ga, 2 3/4" 3 1/4 tons: 7280 psi LC, 9682 psi CIP 12ga, 3" 3 1/2 tons: 7840 psi LC, 10,427 psi CIP 12ga, 3" 4 tons (mag proof): 8960 psi LC, 11,917 psi CIP Note that on the above chart, the only numbers we should focus on are the larger ones, obtained via the modern transducer system--which is how the psi figures in our reloading manuals are obtained. Note also that the guns proofed under the 1954 rules do not reach the American (SAAMI) 12ga standard of 11,500 psi until you get to the 4 ton, mag proof guns. This might be of particular interest to those people shooting "modern" British guns (like Scott 700's) with 2 3/4" chambers and carrying the 3 1/4 tons marking--because they fall about 2,000 psi short of the service pressure for American 12ga factory loads. (And I expect a lot of them have been shooting American factory loads for about half a century.) The current CIP service pressure standard for guns marked 850 bars (or 900 kg) is correct as I gave it above. Those are lead crusher bars. The equivalent proof pressure in CIP (transducer) bars would be 960 bars, with a service pressure of 740 bars or 10,700 psi. So it would appear that the current British proof system represents an increase of about 1,000 psi over the 3 1/4 tons guns under the 1954 system (and nearly 1800 psi over the 3 tons guns). Here's another way to look at it, if you're shooting factory 12ga ammunition: 12ga, 2 1/2" 3 tons gun: use CIP approved shells marked 12-65 12ga, 2 3/4" 3 1/4 or 3" 3 1/2 tons guns: CIP shells marked 12-70 And to paraphrase Will Rogers  The first line appeared in a New York Times column “Slipping the Lariat Over” in Sept. 30, 1923 “All I know is just what I read [on the internet], and that's an alibi for my ignorance.”
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Joined: Dec 2011
Posts: 909 Likes: 43
Sidelock
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Sidelock
Joined: Dec 2011
Posts: 909 Likes: 43 |
Thanks guys. It would seem that even though those 2 1/2 " English hunting loads kick like little mules, they are lower pressure than I thought. Don't tell anybody else though, I've been making pretty good money putting punched out 2.5" guns back on face! :-)
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Joined: Jan 2002
Posts: 11,381 Likes: 106
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 11,381 Likes: 106 |
Here's your post in 2008 Larry. I couldn't go back on DoubleGun past the 2007 discussion but it all probably started before then http://uplandjournal.ipbhost.com/topic/6351-chamber-pressures/Digging through my files, I found the following information--which, although the pages in question do not indicate for sure, I believe came from the Birmingham Proof House. Here we go: 1954 Rules of Proof Service Pressures Converted to Approximate CIP values 12ga, 2 1/2", 3 tons: 6720 psi lead crusher system (LC), 8938 psi transducer (CIP) system 12ga, 2 3/4" 3 1/4 tons: 7280 psi LC, 9682 psi CIP 12ga, 3" 3 1/2 tons: 7840 psi LC, 10,427 psi CIP 12ga, 3" 4 tons (mag proof): 8960 psi LC, 11,917 psi CIP Note that on the above chart, the only numbers we should focus on are the larger ones, obtained via the modern transducer system--which is how the psi figures in our reloading manuals are obtained. Note also that the guns proofed under the 1954 rules do not reach the American (SAAMI) 12ga standard of 11,500 psi until you get to the 4 ton, mag proof guns. This might be of particular interest to those people shooting "modern" British guns (like Scott 700's) with 2 3/4" chambers and carrying the 3 1/4 tons marking--because they fall about 2,000 psi short of the service pressure for American 12ga factory loads. (And I expect a lot of them have been shooting American factory loads for about half a century.) The current CIP service pressure standard for guns marked 850 bars (or 900 kg) is correct as I gave it above. Those are lead crusher bars. The equivalent proof pressure in CIP (transducer) bars would be 960 bars, with a service pressure of 740 bars or 10,700 psi. So it would appear that the current British proof system represents an increase of about 1,000 psi over the 3 1/4 tons guns under the 1954 system (and nearly 1800 psi over the 3 tons guns). Here's another way to look at it, if you're shooting factory 12ga ammunition: 12ga, 2 1/2" 3 tons gun: use CIP approved shells marked 12-65 12ga, 2 3/4" 3 1/4 or 3" 3 1/2 tons guns: CIP shells marked 12-70 And to paraphrase Will Rogers The first line appeared in a New York Times column “Slipping the Lariat Over” in Sept. 30, 1923 “All I know is just what I read [on the internet], and that's an alibi for my ignorance.” Aha. That's where it came from. Now the only remaining fly in the ointment is whether CIP transducers and SAAMI transducers tell the same story. I have a vague recollection of someone posting here that they do not. (If that's correct, then we're still speaking a different language.) But my email from the Birmingham proofmaster says that his values "should be used for comparison with SAAMI transducer values". Which indicates to me that in that particular case, we do seem to be speaking the same language.
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Joined: Jan 2006
Posts: 9,428 Likes: 315
Sidelock
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Sidelock
Joined: Jan 2006
Posts: 9,428 Likes: 315 |
For the 2 guys (you and me) still interested Back in the dark ages of 2006-2007 when we first started trying to understand all this, B&P had a speed/pressure chart with BAR converted to psi by a simple calculation http://carolans.com/R/bp-1/content/Speed-and-Pressure-Chart.pdfThe 16g F2 Classic was listed at 9,867 but actual pressure testing showed it to be 10,500. We assumed the BAR was measured by copper crushers (the CIP standard rather than lead) B&P published a new chart in 2016 and the F2 is now 720 BAR or 10,443 psi http://www.baschieri-pellagri.com/en/catalogo/cartucce+da+caccia/1/1/16.aspx About the same time, Gamebore Traditional Game 16g 28gm (1 oz.) was reported to run 1260 fps at 8122 psi but pressure testing by Tom Armbrust showed it to be 8400 psi. The box was labeled "These cartridges are suitable for use in: 70mm case length: Guns with a chamber length of 2 3/4" or longer, nitro proofed to a service pressure of 3 1/4 tons per square inch (900 kg per square cm) 67 mm case length: Guns with a chamber length of 2 1/2" or longer, nitro proofed to a service pressure of 3 tons per square inch (850 kg per square cm.)" As are CIP shells today. The CIP site is now quite clear that all measurements are by transducer, and reported as BAR. I think we can assume SAAMI and CIP transducers are comparable, but the Brits (being smarter than us colonials and the euros) though no longer using lead crushers are probably using secret transducers with different values just to mess us up 
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Joined: Jan 2002
Posts: 11,381 Likes: 106
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 11,381 Likes: 106 |
Drew, the only problem with the labels on those British shotshell boxes is that they equate service pressure and proof pressure. 3 tons per square inch is a service pressure, but 850 kg (or bar) is a proof pressure. And it's a proof pressure as measured by crushers, not by transducer. So while we're clear on the fact that they're using transducers for their measurements, they continue to use crusher values (and confuse service pressure with proof pressure) on the labels on their shotshell boxes.
I'm convinced it's all an evil plot. Those Brits are probably trying to put the empire back together again.
Last edited by L. Brown; 02/18/18 09:33 AM.
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Joined: Jan 2006
Posts: 9,428 Likes: 315
Sidelock
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Sidelock
Joined: Jan 2006
Posts: 9,428 Likes: 315 |
Indeed “These cartridges, if they are to be fired from standard proof shotguns (ie those proved to 960 bar [transducer] or, previously, 850 bar [crusher]), or magnum proof shotguns (ie those proved to 1370 bar [transducer] or, previously, 1200 bar [crusher]) must not exceed the maximum admissible service pressure of 74 MPa (new units “megapascals”, in place of the old 740 bar) specified by the CIP and measured by means of a piezo-electric transducer.” WHAT?? I feel like Alice, and am giving up "When I use a word," Humpty Dumpty said, in a rather scornful tone, "it means just what I choose it to mean - neither more nor less." "The question is," said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty, "which is to be master - that's all." Lewis Carroll, Through the Looking Glass
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Joined: Nov 2002
Posts: 9,381 Likes: 1
Sidelock
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Sidelock
Joined: Nov 2002
Posts: 9,381 Likes: 1 |
I suspect relevancy of original proof marks on 100 year or any old gun would have to be taken in conjunction with mechanical condition of gun having them. Other than knowing what type of shell the gun was made to handle what do these marks mean to user of such gun today? To put it another way how is value of original proof affected by wear and tear on old gun?
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Joined: Dec 2011
Posts: 909 Likes: 43
Sidelock
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Sidelock
Joined: Dec 2011
Posts: 909 Likes: 43 |
So to sum up what we know for sure, In England and Europe we have government facilities That try to blow up guns. The units of measurement involve crushing , copper, lead, and the use of electric strain gauges calibrated in lbs./sq.in., BAR, and mega-pascals. And there are no mathematical formula to convert one system that we don't understand to one we do. And in the States we have a completely different system relying on manufacturing facilities to try to blow up their own guns so somebody else won't and sue them when a customer tries to do it. And we buy ammunition from sources that make it based on any or all of these systems, but won't share exactly what's going on inside, or even sometimes accurately measure what's the actual outside measurements. And we put all these things together millions of times a year, all over the world, by people who range from experts to not sure which way to stick the bullet in. And from this we have a miniscule number of dangerous incidents. Did I miss anything? And people doubt there is a God and he watches out over us A LOT!
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Joined: Jan 2006
Posts: 9,428 Likes: 315
Sidelock
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Sidelock
Joined: Jan 2006
Posts: 9,428 Likes: 315 |
Well said Mark. God does indeed protect the clueless (Psalm 116:6), but I wouldn’t always count on it!  Proverbs 1:32 (Revdoc Non Inspired Version) "The waywardness of the simple will kill them, and the complacency of fools will destroy them (and their barrels)." Hatcher's Notebook, 1966 https://books.google.com/books?id=yESNUKSg5aMC&pg=PA184&lpg “E.C.” blank powder burns with extreme speed...to give a sharp report when it is not heavily confined. An enthusiast once got hold of some of this powder, being familiar with “E.C.” shotgun powder...and loaded a bunch of shells. To try out his new load he got out his fine Lefever gun, and put up a target in the shooting gallery to get the pattern. There was a terrific detonation, and a big piece was blown out the side of the barrel near the breech, flew across the room and buried itself in a wood bench.
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