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Anyone know of a decent metric conversion to Imperial measurements site. Looking for pressure conversion English Proof 3 tons Sq in to Bar and 3 1/2 tons to Bar

Hotrack

Please see this thread
http://www.16ga.com/forum/viewtopic.php?t=3428
Larry Brown did all the hard work.

Here I'll make it alittle easier.
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PROOF/PRESSURE

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 sq. 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 (3 1/4 tons per sq. inch) 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**

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

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 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 (SAAMI)

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

Standard 1900s loads per LC Smith Hang Tags:
12g 3 dram 1 1/4 oz 1165 fps
16g 2 1/2 dram 1 oz 1165 fps
20g 2 1/4 dram 7/8 oz 1155 fps

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.
The Super-X 2 3/4 inch 3 3/4 dram equiv. 1 1/4 ounce load (1330 fps) was near the SAAMI max. of 11,500 psi.

Baschieri & Pellagri data BUT you must add 500-1000 psi to the reported pressure to get an approximation of the SAAMI equivalent PSI. The 16g F2 Classic is factory listed at 9,867 psi but testing by Tom Armbrust showed it to be 10,500.
http://www.bandpusa.com/files/db_trio.pdf

Gamebore Traditional Game 16g 28gm (1 oz.) is reported to run 1260 fps at 8122 psi but pressure testing by Tom Armbrust showed it to be 8400 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.)"

It's appropriate to view the 3 ton/650 bar/8,939 psi pressure as the maximum service/using pressure rather than the standard/recomended service pressure. The Gamebore loads run below 8500 psi but are 'approved' for use in 3 ton/650 bar service/850 bar proof guns. In light of the age of the wood and metal of classic American and British SxSs, shoot low pressure to save the action, shoot light shot charge/low velocity to spare the wood. It seems reasonable to limit pressure to 8,500 psi, and several commercial loads are available from 5,000- 7,000 psi http://www.doublegunshop.com/forums/ubbt...ge=11#Post31805

BOTTOM LINE: ANY 850 BAR (proof) = 650 BAR service or 3 TON service gun should be fine at pressures under 8500 psi, or 3 1/4 tons less than 9,500 psi.



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



WEIGHT

1 ounce = 0.0625 pound= 28.35 grams

24 gm=.85 oz.=just less than 7/8 oz.

26gm=15/16 oz.

28 gm=1 oz.

30gm=1.06 oz.=1 1/16 oz.

32 gm=1.13 oz.=1 1/8 oz.

34 gm=1.2 oz.=1 1/5 oz.

36 gm=1.27 oz.=just more than 1 1/4 oz.



SHOT SIZES


US UK Italian

mm inches mm inches mm inches

4 3.3 .13 2.8 .11 3.1 .122

5 3.0 .12 2.67 .105 2.9 .1145

6 2.8 .11 2.54 .10 2.7 .1065

7 2.54 .10 2.4 .095 2.5 .0925

8 2.3 .09 2.29 .09 2.3 .091



UK

http://www.kwacs.org.uk/barrels&choke.htm
http://www.hrwscothunt.ndtilda.co.uk/info/data.htm


From the Eley Shooter's Diary, 2005:

British 4 3.1mm, .12", 170/oz

5 2.8mm, .11", 220/oz

6 2.6mm, .10", 270/oz

Note that in sir Gerald Burrard's work "The Modern Shotgun" Appendix III was a work on "The Piezoelectric Pressure Gauge and it's Application to the Measurement of Pressure in Shotguns" by A Watson, B.Sc., F.Inst.P. In this work he discusses the mounting of a piezoelectric (P) gauge & a lead crusher (L) gauge on opposite sides of a pressure bbl, both @ exactly 1.0" from breech giving simultaneous readings of the same shot. After a careful study of these readings the following was stated; "Over the range of pressures usually encountered at the one inch position in shotguns the reaings given by the two gauges are related by the equation; P=1.5L(tons)-.5tons"
These pressures are all given in tons & are the British Long Ton @2240lbs. Working this formula gives the following with all converted to equivelent piezoelectric psi;
3 tons (6,720) = 8,960psi
3¼ tons (7,280) = 9,800psi
3½ tons (7,840) = 10,640psi
4 tons (8,960) = 12,320psi
Note the similarity of these conversions to the pressures given in the 1954 Rules of Proof per the very excellent previous post.

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

Also note this conversion is applicable "Only" to those 1.0" pressures in the normal range of shotgun loads. They are also only applicable to those pressures recorded under the British Crusher system. Other crusher systems would likely be similar, but not necessarily exact. Piezoelectric psi readings are generally considered to be "Exact" & will almost always be higher than crusher pressures. There "May" be a few instances where time lag of the crusher is so low the two give essentially equal readings.
Also "Nota Bene" the difference in the two systems over this limited range varies from 1ton (2240psi) to 1½ton (3360psi). The use of the oft stated 1,000 lbs would thus seem to be useless & in some cases could prove dangerous.

Thanks for the Info

Hotrack

One other factor you have to remember in this quite complicated proof/pressure business: the "tons" markings were for service pressure. In other words, if 3 tons equates to 8900 psi, that's the upper pressure limit of the loads you should be shooting in the gun. The more recent "bars" markings are proof pressures. So, for example, you can't take 850 bars--current CIP standard proof pressure--multiply it by 14.5, and arrive at a pressure limit for your loads. (And you can't do that for another reason anyhow, at least on Brit guns, which is that the "bars" in question are crusher bars, not piezo bars--which means the resulting figure is LUP, not psi.)

It can make your head spin.