doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Shotshell pressure...British vs US

I was looking at this listing..... http://www.gunbroker.com/Auction/ViewItem.aspx?Item=301527910

and it shows on the Hull Cartridge Co. shotshell box minimum recomended barrel strengths. Can anyone translate the British statement for minimum barrel strength that is listed on this box? I would want to shoot these shells in my damascus barreled SxS.

SxS

Looks like they are made for the U.S. market as they are not like the Hull Cartridge Company stuff sold here. I think they copied the same warning as on U.S. boxes about damascus barrels. I've just looked at a similar box I have and the same information is on with the exception of the damascus warning. I would say that if you are using them in a British damascus barrelled gun that is in proof for 2 1/2" nitro stuff then they will be o.k. If in a U.S. damascus unproved gun they I would check with a well qualified gunsmith. Lagopus.....

It's complicated, this is the short version, and you'll find lots more information in old threads using the search function

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

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

That of course is the service pressure of the gun for which the cartridges are suitable. They generally generate pressures quite a bit below that figure. Hull Cartridge Company are usually fairly obliging so it may be possible to e-mail them and find the pressure range of that ammo. They have to batch test frequently to comply with the CIP rules. You should find a batch number somewhere embossed or printed on the carton. Lagopus.....

Note; that many, many years ago Burrard stated that pressure bbls in England had been fitted with both crusher & PE measuring equipment so the pressure could be measured simultaneously by both methods. Within the range of shotgun pressures a workable conversion was arrived at. While not exact it was considered to be "Close Enough" for all practable purposes.
The formula was 1� crusher tons - � = PE tons. Realizing the British ton is the Long ton or 2240lbs then this comes out as follows for PSI;
3x1� - � = 4PE tons
4tons x 2240 = 8960PSI.
Notice this is only 22 PSI different from the figure Drew gave us, certainly within workable range.
The 3� ton pressure of a 2 3/4" chambered British gun would by this same formulla convert to 9,800 PSI
Inso far as I know this formula is applicable "ONLY" for British crusher pressures.

As Drew stated above, the Birmingham Proof House confirms that service pressure for a standard proof (old 850 bars) CIP gun is 10,730 psi. I agree that the Damascus barrel warning must be for the US market. You'll probably find quite a few Brit guns with Damascus barrels, nitro proofs and the 1 1/8 shot charge mark. And you'll undoubtedly find some that have passed reproof and are now marked either 3 tons or 850 bars. If your gun carries any of those marks, you should be good to go with those shells.

As confused as ever:

Mr. Drew Hause: a service pressure of 3 tons per sq. in. =. 8,938 psi service pressure (CIP)

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

Mr. L. Brown: You'll probably find quite a few Brit guns with Damascus barrels, nitro proofs and the 1 1/8 shot charge mark. And you'll undoubtedly find some that have passed reproof and are now marked either 3 tons or 850 bars. If your gun carries any of those marks, you should be good to go with those shells.

So am I to understand that:

1 1/8 oz. = 3 tons service pressure = 850 bars proof pressure (Mr. L. Brown) = 10,730 psi service pressure (Mr. Drew Hause)

However

3 tons = 8,938 psi. service pressure (Mr. Drew Hause).

Mr. 2-piper: 3 1/4 tons service pressure is more than 3 tons service pressure (he did not say so but his math made me understand that - for which I am only too happy to stand corrected) against both 2 1/2 and 2 3/4 in. standard loads being the same service pressure as per CIP today. Where as previously 1 1/4 oz. loads were by definition 2 3/4 in. non magnum loads in the UK not to be used in guns marked 2 1/2in. or 1 1/8 oz.

My apologies if I have appeared rude to anyone as that was not my intention and without taking anything away from the original poster who simply asked if a certain cartridge could be used in his Damascus barreled gun!

I am probably reading all this right to left instead of left to right but then most double guns are geared that way!

All the best

Skeeterbd

http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=33387&page=1

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 square 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 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**

Per the 1954 Rules of Proof, here are the equivalent CIP 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 (CIP)

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

The SAAMI psi conversion for the 1954 TONS measurement is different from the 1989 BAR measurement.
Bottom line: ANY 850 BAR or 3 TONS gun should be fine at pressures under 8500, or 3 1/4 tons less than 9,500 psi

SxS, quite often--but not always--British shotshell boxes will provide you with all the information you need, concerning which shells should be fired in which guns. For example, I'm looking at a box of Gamebore Traditional Game shotshells, 28 gram, 2 1/2", 20 gauge. On the box I find:

"WARNING. Please note these cartridges are suitable for use in:
GAME (65/67mm) LOADS: Guns with a chamber length of 2 1/2" (65/67mm) or longer, nitro proofed to a service pressure of 3 tons/sq inch (850 kg/sq cm)."

There's one small glitch in that information, in that 850 kg (or bars) is actually the proof pressure, not the service pressure. But what they're telling you is that those shells can be used in any guns marked either 3 tons or 850 bars. Helpful of them to provide all that information.