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

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)