doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 3 inch CIP v 3 inch SAAMI pressures

Just fiddling through the CIP Homologation pages I came across these shotshell pressure tables:

CIP Shotshell Pressures

This indicates that the max service pressure for 3 inch CIP shells is 1050 bar = 15229 PSI and the proof pressure is 19245 PSI.

SAAMI service pressures are 11500 PSI across all 12 gauge cartridges except the 3 1/2 inch cartridges. I believe SAAMI proof pressures are in the 20000 PSI range.

That is some difference between the two Max service pressures.

I have probably read the figures all wrong but in case I haven't then my questions are:

1. Are CIP 3 inch cartridges usable and safe in US made 3 inch chambered guns? (given that the proof pressures are similar they should be).

2. Have CIP superior proof pressures changed from the original British Proof house nitro proof pressures for 3 inch 12 ga. cartridges ( as in "back in Greener's day!)? (The standard proof apparently has not).

3. Given that max pressures for SAAMI specs 3 inch cartridges are only 1000 or so PSI more than the standard CIP proof at 740 bar = 10730 PSI are they safe to be shot in three inch chambered British guns with the older 1 1/2 oz = 3 1/2 tons per square inch proofs. These are built much stouter than the typical English game gun and obviously proofed for higher pressures.This does assume all guns are in proof.

4. Does anyone know what the proof pressures were for the 1 1/2 oz = 3 1/2 ton per sq. inch proof pressure was?

There is a blackpowder proof charge for 3 inch nitro proof given in Greener's book. I have no way of measuring the pressure generated nor even of getting blackpowder. Has anyone ever tried this charge for pressure?

Thanks for any and all observations and corrections.

All the best

Skeeterbd

I own a 1906 Purdey That was sleeved, presumably by Purdey or Teague for Purdey, so that the owner then could use British 3 inch shells for waterfowl. The bbls show all the proper proofmarks.

Would American 3 inchers be safe ?

danc

Skeeter, the 740 bar pressure you mention as proof pressure is in fact the service pressure for 12 gauge guns of less than 76mm chamber, ie non magnums.

If the chamber is 76mm then the gun must be submitted for compulsory proof at 1370 bar. The same standard is vountary for 70mm chambered guns. The compulsory proof for standard chambers is 960 bar.

This leads to some confusion in Europe because there are 70mm shells generating 1050 magnum service pressures, but these are marked on each shell (thankfully!), not just the box. To add to the confusion Proof Houses do not have a clear numerical indication of pressure, most having a stamp which the public are expected to interpret.

Proof pressure have changed over the years, the latest changes came about in the early 1990s when magnum proof pressure increased from 1200 to 1370 bar and regular proof from 900 to 960 bar.

You can get the CIP table showing proof and service pressures for each gauge from the CIP site.

Crowley, what do these "proper" proof marks say?

The rule of thumb for us in Europe is that guns are proofed at service pressure plus 30 per cent. Therefore service pressure is proof pressure minus 25 per cent. And bear in mind the British and Russian practice of stamping service pressure on their guns, not proof pressure as the rest do. So on a British gun the stamp 3 1/4 tons, or in a Russian gun the 750mpa are the service pressures, not the proof pressures. On all others the pressue indicated on the gun is the proof pressure and must be reduced by 25 per cent to figure the service pressure.

Proof pressure is the actual pressure the gun withstood during testing. Service pressure is the pressure it is meant to withstand in regular use.

Keeping it simple tends to keep it safe too.

Shotgunlover

Thanks for you kind observations.

I have looked at the list of CIP proof pressures. I do know that the 740 bars is the service pressure for standard proof guns. I obviously did not state it in my post correctly.

If proof pressures have changed from 1200 bars to 1370 bars then was the older 1200 bars the equivalent of the old 3 inch proof of 3 1/2 tons per square inch? (To further add a twist: was the 1200 bar pressure measured by transducers or was it LUP?)

1200 bar (transducer) should lead to a 900 bar service pressure (13050 PSI)

My real question was that are American three inch shells at 11500 PSI service pressure safe in older (in proof) 3 inch chambered British guns?

The standard proof service pressure is 10730 PSI. The maximum allowable pressure in individual loads is 850 bar as per the CIP tables(while maintaining a max average pressure of 740 bar).

850 bar is 12328 PSI. So the odd 11500 PSI cartridge of appropriate length in the appropriate chamber ( i.e. 2 3/4 inch shell in 2 3/4 inch chamber) will be handled with ease even by standard proof guns.

So by that "logic" the much heavier proof and stouter build of even older 3" chambered ( 3 1/2 tons per square inch service pressure) British guns should allow them to easily handle American 3 inch shells at 11500 PSI (792 bar, say 800 bar)!

As always ready to be shot down in flames.

Thanks again for your interest and clarification.

All the best

Skeeterbd

Some confusion here--no surprise at all!--concerning CIP proof. The CIP "change" in proof pressures in the early 90's was, in fact, only a change in the way pressure is measured, not the pressure itself. 850 bar standard/1200 bar superior or magnum continued to be stamped on British guns until 2006, at which point the bar figures were dropped entirely and replaced by STD under one crown for standard, SUP under 2 crowns for superior. What happened in the early 90's is that the CIP countries, which had been using the old crusher system of measuring pressure, switched to the modern electronic transducer system. Transducers--which SAAMI had been using for quite some time before CIP countries converted--give different pressure readings than crushers for the same shells. The old crusher readings, in SAAMI terminology, are expressed as LUP (lead units of pressure), which you'll see in some reloading manuals. Transducer readings are psi.

So CIP didn't really increase proof or service pressure standards. All they did was express it in numbers derived from transducers rather than crushers. And the transducer numbers are higher (just as psi values are higher than LUP), which makes it look as if pressures were increased. To further add to the confusion, the Spanish proofhouse started marking their guns with the new transducer numbers, while the British proofhouses continued to use the old crusher numbers for their proofmarks--even though both countries converted to the transducer system in the early 90's.

No wonder there's confusion on this subject!

Note also that in perusing many "Old" US reloading manuals pressures will be given in PSI which were truly LUP's.
The old British 3� Ton pressure was service pressure taken by the crusher method. It translates to approximately 10,640 PSI, so about 1,000 PSI lower than 3" SAAMI pressures.

I have a Lyman reloading manual from 1984 that expresses all pressure values in LUP, and in the section on pressure, describes in detail the crusher method of measurement. The information I have from SAAMI includes a data sheet from 1984, which refers to the crusher method as "the older method of pressure measurement". And the current SAAMI pressure tables date from 1992 (all psi). I'm not entirely clear on when we started using transducers here in the States, but it would appear that there was a transition period. Much like the conversion from the old short chambers to 2 3/4" in the years before WWII, it didn't happen all at once.

Thanks for the replies L Brown and 2 piper.2 piper:

From what I understand, if 3 tons per sq. inch is equal to 740 bars (transducer) which is 10730 PSI then 3 1/2 tons per sq. inch must be greater than 10640 PSI (transducer). I believe that crusher pressures don't translate directly to transducer PSI and give much lower than true figures if the usual conversion formulae are used.

See L Brown above, viz: "So CIP didn't really increase proof or service pressure standards. All they did was express it in numbers derived from transducers rather than crushers. And the transducer numbers are higher (just as psi values are higher than LUP), which makes it look as if pressures were increased"

I am as usual probably wrong.

All the best

Skeeterbd

Skeeterbd;
I am not so certain that 3 tons & 740 Bar are equal. back while the Tons system was still in use Burrard reported that simultaneous pressure tests had been run using both lead crushers & Piezo Electric transducers & a fromua worked out which within the range of shotgun pressures "Only" would be very close. Close enough in fact to avoid trouble from its use. The formula was Crusher Tons times 1� minus 1/2 ton = Transducer Tons. Thus 3 x 1.5 = 4.5; 4.5 - .5 = 4. As the Ton here is the 2240 lb long ton then 4 x 2240 = 8,960 PSI. Using the same formula 3� Tons = 9,800 PSI, 3� tons =10,640 & 4 tons = 12,320 PSI.
From what knowledge I have of the subject these do indeed seem to be very close conversions. It is of course true that crusher pressures do not translate directly to transducer PSI. "IF" they did then 3 Tons would =6,720 PSSI & 3� Tons would = 7,840. It is also obvious that the act of adding 1,000 lbs to the crusher reading is not going to be close either. Both of these are more than 2,000 lbs off the crusher reading.

Skeeter, I can't confirm the tons values in psi either. I can do that with the later 850 bar proof/650 bar service pressure guns (crusher figures). Got it straight from the Birmingham proofhouse that the 650 bar figure is actually 740 bar transducer, which is the source of that 10,730 psi service pressure figure for CIP standard proof guns, for the last 25 years or so. Things were confusing during the "tons" era because the Brits marked their 2 1/2" guns 3 tons and their 2 3/4" guns 3 1/4 tons--which is only an 8.5% increase in service pressure. That's not nearly enough to make the jump from standard to superior/magnum loads. But . . . if 3 tons does actually work out to 10,730 psi--although I'm not sure it does--then 3 1/4 would be very close to our SAAMI service pressure of 11,500 psi. And those 2 3/4", 3 1/4 ton Brit 12's were marketed in the states. Mostly Webley & Scott 700's.

Yet another area where things are a bit murky.

2 piper

Thanks again for your reply.

I know that Burrard knew what he was talking about. However have a look at the following:

You will have to open it with Adobe reader.

Rottweil Tiger Shotshell Data



If you scroll down to page two you will see that it states:

"The Rottweil Tiger is a very versatile usable shotshell. With a case length of 67.5 mm, it is designed for shotguns with the formerly common chamber length of 65.0 mm on the one hand and works very reliably in the critical semi-automatic shotguns on the other hand."

Since it is safe to use in a 65mm = 2 1/2 inch chamber and being a modern CIP shotshell it has a service pressure of 740 bar = 10730 PSI. From this I presume it is usable in the old 2 1/2 inch chambered 3 tons per sq. inch guns, particularly as the blurb refers to "formerly common" chamber lengths, and especially as these guns are very much in use today with British CIP shells of the same pressure standards in the UK.

From this I infer that the if 10730 PSI is safe to use in a 2 1/2 inch chambered 3 tons per square inch service pressure proofed gun then the safe usable pressure (service pressure) in a heavier proofed 3 inch chambered 3 1/2 tons per sq. inch service pressure gun must be substantially higher than 10730 PSI. 3 1/2 tons is 16.67% higher than 3 tons (to state the obvious). Thus I infer that 3 1/2 tons service pressure is higher than 11500 PSI (10730 PSI + 16.67 % of 10730 PSI = 12518.69 PSI)


Surely if CIP proof 2 1/2 inch cartridges aren't meant for the4 older extant 3 tonners then they would say sop on the box. they say the opposite. What say you?

L Brown
I posted the above without reading your post which probably crossed mine.
I agree that 3 1/4 tons is not enough for magnum proof (especially CIP magnum proof at 1370 bar with service pressures of 1050 bar) but it is near 11500. PSI. So 3 1/2 tons must be higher and therefore guns so marked, in proof, with 3 inch chambers should be all right with SAAMI 3 inch cartridges.

All the best

Skeeterbd

Skeeter, per comments from a previous Birmingham proofmaster, who overlapped the transition from the 1925 rules of proof to the 1954 rules ("tons" era), we know that proof pressures did not change as a result. I've never seen it stated for certain that 2 1/2" service pressure was the same under the 1954 rules as it was under the later 1980's rules (850 bar guns), but like you, I've read on Brit shotshell boxes that 2 1/2"/65MM/67.5MM shells are good to go in 3 ton OR 850 bar guns. That certainly makes it sound as if the service pressure is the same . . . or else those shells are loaded to the old 3 ton specifications, which would mean they're also OK in guns proofed under the 1925 rules.

This is a 8 year old thread, but it is the first thread linked when doing a Google search for "CIP Shotshell Pressure Standards" SO to help future searchers:

The Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives standards were ratified in 1969.
https://www.cip-bobp.org/en/cip
Click on “Proof” for videos of the proof process and examples of proof failures

https://bobp.cip-bobp.org/en/tdcc_public?page=1&cartridge_type_id=7





12g 50mm, 65mm, and 70mm “Standard Proof” lead or steel (limited to no larger than 3.25 mm and max. fps 1,300).
Numbers are transducer BAR converted to PSI.
Maximum Average (SERVICE) Pressure 740 BAR = 10,733 psi;
Maximum Statistical Individual Pressure 850 BAR = 12,328 psi
Mean PROOF Pressure 930 BAR = 13,489 psi
(The original 1984 chart, which was revised in 1990, indicates 12g PROOF 960 BAR = 13,924 psi. The number was revised to 930 BAR)

12g 3” & 3 1/2” “High performance/Superior Proof”
Maximum Average (Service) Pressure 1050 BAR = 15,229 psi
Maximum statistical individual pressure 1200 BAR = 17,405 psi
Magnum proof 1320 BAR = 19,145 psi

12g STEEL regulations: the barrels should carry the High Performance Steel Fleur de Lys stamp and be marked “Steel Shot”

Both 65 and 70 mm 16g standard is SERVICE 780 BAR or 11,313 psi;
MSIP 900 BAR or 13,053 psi;
PROOF 980 BAR or 14,214 psi.
(The original 1984 chart indicates 16g PROOF 1020 BAR = 14,794 psi. The number was revised to 980 BAR in 2006.)

Both 65 and 70 mm 20g standard is SERVICE 830 BAR or 12,038 psi;
MSIP 950 BAR or 13,779 psi;
PROOF 1040 BAR or 15,084 psi.
(The original 1984 chart indicates 20g PROOF 1080 BAR = 15,664 psi. The number was revised to 1040 BAR 11-2021.)

Italy is a member of CIP, but according to Gerhard Wirnsberger, “The Standard Directory of Proof Marks” in 1962 established Standard Proof at 12,801 psi (probably by LUP/crushers) indicated by a ‘star over PSF’ AND “Superior Proof” at 17,637 psi, with ‘2 stars over PSF’ marks.
“Superior Proof” is mandatory for chambers longer than 70mm = 2 3/4”.

Great Britain adopted the 1969 Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives standards March 1, 1980.
BAR however was not introduced until 1989, and the imperial proof marks could be requested from 1984 to 1989 using the Tons SERVICE pressure while the metric version used the Kg PROOF pressure.

Pre-CIP Spanish Proof
See https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=568600

850 kg/cm2 proof was commonly used for entry level Basque 12/70 guns of the 50's through the early 70's. Better grades carried 900 or 1000 kg/cm2 proof with some 12/70 pigeon guns 1200 kg/cm2.

850 kg/cm2 proof = 12,090 psi for a service pressure of 566.6 kg/cm2 or 8060 psi BUT as measured by lead crushers, so by modern piezo transducers the pressure would be + 10 - 14% or about 9000 psi
900 kg/cm2 proof = 12,801 for a 600 kg/cm2 = 8534 psi service pressure + 10 – 14% or about 9500 psi
1000 kg/cm2 proof = 14,223 psi for a service load of 9,473 psi + 10 – 14% or about 10,500 psi
1200 kg/cm2 proof = 17,068 psi for a service load of 800 kg/cm2 = 11,380 + 10 – 14% or about 12,500 psi

This is the question which never dies. These are maximum service pressures we are looking at, based on proof pressures for current, 1989-date proofed guns?

Proof pressures and service loads are complex for a number of reasons. We are dealing with multiple proof periods and first we need to figure out when your gun was proofed, to understand what pressure it was proofed for. During some periods only chambers and shot load were marked, or tons per square inch, or now in bars. British proof markings: The "tons" mark (which is service pressure) was not used until 1954, 1954-1989. 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. Post 1989 they went to bars. I thought standard proof in 1989 and after, was 850 bars with a service pressure of 650 bars, not 740 bars. As per Larry Brown "850 bar proof/650 bar service pressure guns (were) (crusher figures). Got it straight from the Birmingham proofhouse that the 650 bar figure is actually 740 bar transducer, which is the source of that 10,730 psi service pressure" I guess I have been over cautious using 650 instead of 740.

Current CIP/ British standard proof is 850 Bar for 2 1/2" and 2 3/4"?
Standard service pressure 2 1/2" and 2 3/4" is 740 bar, 10,733 which is about the old 3 1/2 tons level.


Current CIP Superior proof for 3" is 1200 bar?
Standard service pressure for 3", 1050 bar which is 15,229, which seems very high. SAAMI for 3 1/2" is only 14,000.


Under the 1954-1989 rules I think 3" were proofed at 4 tons squared but some might have been 3 1/2 tons.

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 are all for "upper" service pressure loads, many loads are well under these levels.

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. I was told my 3" was 4 tons and it is so marked.

Bottom line:
2 1/2" & 2 3/4" current proof, (post 1989), 10,733 safe.
3" current proof, (post 1989), 15,229 safe.

2 1/2" & 2 3/4" proof 1954-1989, 3 tons 8,938 safe.
2 3/4" proof 1954-1989, 3 1/4 tons 9,682 safe.
2 3/4" proof 1954-1989, 3 1/2 tons 10,427 safe.
3" proof 1954-1989, 4 tons 11,917 safe.

Pre 1954 you need to figure where your gun proof lines up with 1954 rules.


https://bobp.cip-bobp.org/en/tdcc_public?page=1&cartridge_type_id=7

Jon: CIP Superior PROOF is 1370 BAR = 19,870 psi which is essentially the SAAMI standard. From
https://saami.org/wp-content/uploads/2019/01/SAAMI-Z299.2-Shotshell-Approved-2015-08-31.pdf

Proof loads:
If a manufacturer uses a SAAMI proof loads, then the gun will be proofed by a lot of no less than 10 shots of ammo loaded to a maximum proof pressure of 20,500 psi +/- 900 – 4600 psi, or uber max of 25,100 PSI; and, will be similarly a MINIMUM average proof pressure of 19,000 PSI +/- 900 – 4600 psi for an absolute minimum proof of 14,400 PSI.

And it is important to recognize the acceptable deviation in both fps and psi
Load velocity can vary by +/- 90 fps for both game and target loads.
Load pressure
Maximum average pressure for 2 3/4" and 3” shotgun shells will be 11,500 PSI +/- 900 psi, with some maximum extreme variability not to exceed an uber-max of 12,500 psi +/-900 psi

re: post-1925 and post-1954 proof pressures
“Proof Tests and Proof Marks: Practices of Manufacturers in the United States”, 1934.
Limits are based on the 1925 British Rules of Proof. Long tons are converted to PSI simply by X 2240, and the numbers were measured by LUP so require adding 10 - 14% for modern piezo transducer numbers.



Vic Venters (Jan/Feb 2009 Shooting Sportsman) quoted Roger Lees (Birmingham Proofmaster, both before and after the switch to the 1954 Rules): “The proof loads now set down in [the 1954 Rules] are almost in every instance the proof loading in use under the 1925 rules. In general it may be said that under the new Rules of Proof no arm will receive a more severe proof than hitherto.”

John Brindle, author of Shotgun Shooting: Techniques & Technology published a review of Proof and Service pressures in Part 5 of his series in The Double Gun Journal, “Black Powder & Smokeless, Damascus & Steel”; Volume 5, Issue 3, 1994, “Some Modern Fallacies Part 5”, p. 11.
His estimated post-1954 but pre-CIP standard pressures by LUP converted to piezo transducer PSI

....................Standard Service.....Max. Service.....Proof
12g 2 1/2”...........6,800 psi............8,800 psi......12,250 psi
12g 2 3/4”...........7,800 psi............9,800 psi......14,050 psi
(CIP 2 3/4”).........10,733 psi...........12,328 psi.....13,489 psi
16g 2 1/2”...........7,300 psi............9,300 psi.......13,150 psi
16g 2 3/4”...........7,800 psi............9,800 psi.......14,050 psi


The case label with a c. 1880 William Sumners, Liverpool 12b specified Curtis & Harvey No. 5 Black Powder:
“Light” - 2 3/4 Dram with 1 oz. shot = 1180 fps
“Medium” - 3 Dram with 1 1/8 oz. shot = 1200 fps
“Heavy” - 3 1/4 Dram with 1 1/4 oz/ shot = 1220 fps
Understanding that pressures generated by Black Powder are lower than that of Dense Smokeless, that would still be a good guide.

Assuming solid stock wood, unmolested barrels and mechanical integrity, I think it would be reasonable to limit a light weight vintage 12g British game gun marked 850 BAR or 3 TONS to loads generating less than 8500 PSI; or 900 BAR or 3 1/4 TONS less than 9,500 PSI or 1 1/8 oz. 3 Dr. Eq. (1200 fps).

These are Ithaca's recommendations from 1901



And Fox's from 1914



Standard loads found on L.C. Smith hang tags:
12 gauge.....3 dram.....1 1/4 oz. shot @ 1165 fps (1887 - about 1920)
................3 dram.....1 1/8 oz. shot @ 1200 fps (after about 1920)
16 gauge.....2 1/2 dram.....1 oz. shot @ 1165 fps (introduced 1896)
20 gauge.....2 1/4 dram.....7/8 oz. shot @ 1155 fps (introduced 1907)

Drew, I was told post 1989 service pressure were 650 bar but that was using crusher values, when converted to transducer they become a 740 bar level. Is that how you interpret this data. 740 bar in transducer measure which is 10,733 psi. This would be service pressure, not the lower conversion of 650.

I understand superior proofs are much higher.

You are correct Jon that Great Britain continued using LUP to measure BAR until 1989.
650 BAR by LUP + 10 - 14% to convert to transducer BAR
650 X .14 = 91; 650 + 90 = 740
740 BAR (by transducers) = 10,733 psi

“Eley Shooter's Diary 2005” stated “The later transducer system uplifts the (PSI by LUP) values by approx. 14%.”
I assume Eley did simultaneous lead crusher and piezo transducer measurements since there is no formula for converting crusher numbers to transducer numbers?

Bro. Larry's conversation with the Birmingham Proof House in 2001 confirmed that they converted Tons to psi simply by Tons x 2240 x 1.33