doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Help needed on pressures of modern loads?

PULLEEEEZ, somebody has to have the answer to this question (which is what most of us just want to know):

Shells at what PSI (service pressure) was it originally designed to shoot?
20' gun marked 1 oz
20' gun marked 1 1/8 oz
60' gun marked 3 TON
90' gun marked 850 BAR
90' gun marked 900 BAR

WHY does this have to be so hard-BUT I might have something important here:

The B&P Speed/Pressure Chart shows the 16g F2 Classic to have a psi of 9,867 BUT ACTUALLY TESTING by Armbrust showed it to be 10,500 psi, and I found the load quite 'hot' in terms of recoil (I know, I know, pressure does not equal recoil!)
It looks like B&P is not using the transducer SAAMI method to report pressure, which explains why all their BAR-PSI data fits the 1 bar=14.50377 psi conversion.

I'm thinking the bottom line here is going to be:
1. Ain't no way to get from the British LUP/CIP Crusher BAR/PSI to the Piezoelectric transducer SAAMI PSI.
2. A service pressure of 3 tons per sq. in.= Birmingham/CIP proof pressure of 850 kg per sq. cm. (BAR)= SAAMI proof pressure of 13,920 PSI= SAAMI service (using) pressure of 10,730 PSI= 650 BAR CIP service pressure.
3. BUT guns proofed at 3 tons service or 850 bar proof were designed to shoot shells at SAAMI pressure less than 8,500 psi.

I think Bro Larry has cleared up this murky mess and hope this is the 'final' word:

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 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 kilograms per square centimetre 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 (3 tons per sq. inch)
2 3/4" chambered may be proofed 900 bar (3 1/4 tons per sq. inch) or higher.

**650 bars or 3 TONS is standard CIP (British and European) service pressure for shells designed for guns proofed at the CIP standard of 850 bars**
**A service pressure of 3 tons per sq. in. =European proof pressure of 850 kg per sq. cm. (BAR)= 13,920 psi proof pressure= 10,730 psi service pressure= 650 BAR service pressure**

For comparison, here's data from actual pressure testing:
3 Dr.Eq. 1 1/8 oz. Winchester Trap Load1,202 fps 9,600 psi

Winchester AA Xtra-Lite 1 oz WAAL12
1189 fps 8000 psi

The 12g 2 5/8" 1 1/8 oz. 3 1/4 Dram Eq (1295 fps) load of the 1920s ran about 10,500 psi.

Baschieri & Pellagri data (keep in mind that 650 bar is the service (using) pressure for guns with proof of 850 bar) BUT you must add about 1000 to the reported pressure to get an approximation of the SAAMI equivalent PSI.
http://www.bandpusa.com/files/db_trio.pdf

Gamebore Traditional Game 16g 28gm (1 oz.) is 1260 fps at 8122 psi. The box is 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.)"

Recoil is not necessarily related to pressure, but in light of the age of the wood of classic American and British SxSs, it seems reasonable to limit pressure to 8,500-9,000 psi, and several commercial loads are available from 5,000- 7,000 psi http://www.doublegunshop.com/forums/ubbt...ge=11#Post31805

ANSI/SAAMI Shotgun Pressure Specifications (Maximum Average Pressure in PSI)
All Piezo measurements unless specified)
Cartridge Maximum Average pressure
10 gauge 11,000 (all)
12 gauge 11,5000 (all but 3 1/2" mag)
12 gauge 3 1/2" mag 14,000
16 gauge 11,500 (all)
20 Gauge 12,000 (all)
28 gauge 12,500 (all)
.410 Bore 2 1/2" 12,500
.410 Bore 3" 13,500

Boy, oh boy, oh boy.......I had no idea the can was that large or there were that many worms.

Thanks to efforts of all and especially to Revdoc's persistence and Mr. Brown's patience, at least I got a solid education on this topic. Hopefully the top is tightly sealed, but I am sure other neophytes like myself are sure to bring it up in future.

Is there anyway to archive all this so you folks can refer that soul to this thread?

We can just link the thread http://doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=33387&page=1&fpart=4

AND I've got the 'final word' (I hope) saved as an e-mail.
Bro Larry and I must have had 10 e-mails back and forth and many thanks for his willingness to share his hard earned knowledge and his 'long-suffering' spirit with us pea brains

Well if a 3 ton (6720 psi) crusher service pressure is equivelent to "10,730 psi (service)" that means it gained 4,010 psi (+60%) in the conversion. I for one am not sure we have all the last words on this subject. Personally I believe the 8960 psi figure is much more realistic & on those guns proofed to 1 1/8oz or 3ton I will stay below 9,000 psi.

What precisely are the Remington proof loads employed by Sherman Bell (which yielded typically 18000psi in his pressure barrel prior to the damascus hijinks) used for at Remington? I assumed they were the top-end proof load for 2 2/4" 12 gauge under SAAMI standards, correct or not? Also seems we've got more than one boiled-down bottom line for historical British and CIP; I guess I'll stick to what I've been doing as I'm still typing with 10.

jack

Miller, I don't believe I equated a 3 ton service pressure to 10,730 psi. The Birmingham Proof house DID equate a 650 bar service pressure to 10,730 psi. I seem to recall that proof and service pressure did not change when the Brits converted from the "tons" markings to bars--but I can't verify that. Probably time that I check with the proof house on the "tons" guns and see what they have to say.

But I certainly agree with staying below 9,000 psi on older Brit guns. That's what I do myself, with my Scott-made Army & Navy guns, from the 1930's.

This was in responce to my post stating the "Older" 3 ton service pressure had been shown by "Simultaneous" crusher & tranducer readings to give an "Actual" reading of about 8960psi.
""IF"" the actual pressures used have not changed then I read that as saying those old pressures were in fact 10,730 "Actual" psi's. Peresonally I need a litle more proof to show they were. I did state verbatin where my figures relating 3 ton to 8960psi derived from. You strongly implied they were all wrong & you had the final word from the Birmingham Proof House. However everything you quoted was for post 80's "Metric" figures. I do not believe these to be totally applicable to the earlier proofs, but could possibly be proved wrong. If so then 10,730 it is.