Joined: 28 Dec 2005
Location: Glendale, AZ
Here is a more concise version, and I am simply a collector and organizer of the data that Larry Brown, the Google guy, Dave Noreen, and many others have contributed.
I'm most happy to correct anything that can be documented to be in error.
Summary of c. 1895 - 1920 pressures, extrapolated to modern piezo transducer numbers
Reported pressures are converted to modern piezo transducer numbers using Burrard’s formula if originally expressed as Tons/sq. inch by LUP (Lead [Crusher] Units Pressure), or by adding 10-14% if PSI by LUP
c. 1900: The “standard” U.S. 12g field and inanimate target load was 1 1/4 oz. shot with 3 1/4 Dram Equivalent (1220 fps) of Bulk Smokeless in a 2 5/8" or 2 3/4" case with a modern transducer pressure of 8000 - 9500 psi.
Just before WWI: The “standard” U.S. 12g field and inanimate target load was 1 1/8 oz. shot with 3 Dr. Eq. (1200 fps) Dense Smokeless in a 2 3/4" case with a transducer pressure of 8,500 - 10,000 psi.
1 1/8 oz. 3 Drams (1200 fps) of DuPont FFFg Black Powder (82 grains) is about 5000 psi.
1 1/8 oz. 3 Drams (82 gr) Curtis & Harvey’s No. 4, T.S. Black Powder (similar but not equivalent to FFg) was about 6500 psi.
1 1/8 oz. 3 Dram Equivalent of BULK Smokeless was 6500 - 7500 psi.
1 1/8 oz. 3 Dr. Eq. of DENSE Smokeless was 8,500 - 10,000 psi.
1 1/8 oz. 3 1/4 Dr. Eq. BULK Smokeless was about 8500 psi.
1 1/8 oz. 3 1/4 Dr. Eq. DENSE Smokeless was 9500 - 10,500 psi.
1 1/4 oz. 3 1/2 Dr. Eq. BULK Smokeless was about 11,750 psi
1 1/4 oz. 3 1/2 Dr. Eq. DENSE Smokeless was about 12,600 psi
The modern SAAMI 12g maximum 2 3/4" and 3" pressure is 11,500 psi
1 oz. 2 3/4 Dr. Eq. BULK Smokeless was about 7000 psi.
7/8 oz. 2 1/2 Dr. Eq. DENSE Smokeless was about 11,000 psi.
7/8 oz. 2 1/2 Dr. Eq. BULK Smokeless was 8000-9000 psi
British Nitro Loads Sporting Guns and Gunpowders: Comprising a Selection from Reports of Experiments, and Other Articles Published in the "Field" Newspaper, Relative to Firearms and Explosives, Volumes 1-2, 1897
“New Rules of Proof”
“Under the 1896 Supplementary Nitro Proof Rules, the Nitro Proof Charge was not fixed. It could be changed by the Proof Houses as existing powders changed or new products released. The Proof Houses would determine the charge in order to keep the pressure 80 - 100% above that of the Service Charge.”
Pressures were measured using crushers (LUP) reported in pounds/ sq. inch and modern piezoelectric transducer pressures would be about 10 - 14% higher.
For a time the British indicated the load for which the gun was designed.
42 grains = 3 Drams "E.C." with 1 1/8 oz. shot
Or on the hang tag. 1906 H&H
42 grains Schultz = 3 dram
1904-1925 only the shot charge and “Nitro Proof” were stamped.
The standard 2 1/2” 12g British load according to the 1907 edition of Greener's The Gun was 1 1/8 oz. 3 1/4 dram (1255 fps).
1897 - 1903 the Belgians provided specific load instructions stamped on the barrels.
Pre-1924 Manufacture Liegeoise d' Armes a Feu 16g
Bore 17.0 mm = .669";
Right choke 16.9mm = .665= Improved Cylinder; Left choke 16.4mm = .646 = Improved Modified
Proved with E.C. No. 3 - New E.C. (Improved) No. 3 was Bulk Smokeless powder and was introduced in the U.S. in 1904; 11 grains = 1 dram equivalent.
Load markings: 1.81 grams "poudre" = 28 grains; E.C. No. 3, Walsrode Gray or Mullerite No. 2 = 2 1/2 Dram Equivalent.
24.5 grams "plombs" (lead) shot is 7/8 oz.
A 12g intended for the U.S. market with "E.C. No. 3", a 33 grain bulk powder = 3 Dram, with 1 1/8 oz. shot
The U.S. makers listed appropriate loads on Hang Tags:
Standard loads found on L.C. Smith hang tags:
12 gauge.....3 dram.....1 1/4 oz. shot (1887 - about 1920)
..................3 dram.....1 1/8 oz. shot (after about 1920)
16 gauge.....2 1/2 dram..1 oz. shot (introduced 1896)
20 gauge.....2 1/4 dram..7/8 oz. shot (introduced 1907)
And in their catalogs:
1914 A.H. Fox Catalog courtesy of David Noreen
Just before WWI, things got MUCH more complicated with a great variety of Bulk and Dense Smokeless powders, with different grain Dram Equivalents.
Major Sir Gerald Burrard in the 1944/1947 Second Edition of The Modern Shotgun, Vol. III “The Gun and the Cartridge”, states during WWI the standard 12g load was dropped by law (to conserve the supplies of lead and powder) to 1 oz. and 3 Dr. Eq.
After the War, the standard for 2 1/2” shells became 1 1/16 oz. with 42 grains (Old) Schultze Bulk (3 Dram), 36 grains “E.C. (Improved)” or 33 grains Imperial Chemical Industries (Eley & Kynoch Cartridges) Dense Smokeless Diamond powder.
In the 1925 British Proof House revisions, the 2 1/2” & 2 5/8” 12g service load was reduced to 3 Drams with 1 1/8 oz. shot with a mean service pressure of 3 1/4 (long) tons = 9,682 psi by Burrard's conversion formula. Until the 1954 revision, only the chamber length was marked.
After the 1924 Belgian Proof House revisions, a Certificat d’epreuve could be issued and specified:
“The pressure developed, measured by crusher type device international standard, lower or equal to 600 kg per square centimeter for sizes 16, l2, 10, 8 & 4; 670 kg per square inch for sizes 20, 24 and smaller.”
600 kg/cm2 = 8534 psi SERVICE pressure;
670 kg/cm2 = 9530 psi SERVICE pressure
+ 10% by piezoelectric transducer measurement.
20 g was PROVED at 1000 kg/cm2 = 14,223 psi
12g PROVED at 900 kg/cm2 = 12,801 psi
Modern transducer numbers for 20g would be close to 15,500 psi; 12g about 14,000 psi.
In the 1954 British Rules of Proof the service pressure was now expressed in TONS and was measured by LUP.
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.”
The equivalent transducer values courtesy of Larry Brown, per the Birmingham Proof House are as follows:
3 tons/ sq. inch = 8,938 psi
(Burrard's conversion formula to convert TONS per square inch expressed as LUP to modern piezoelectric transducer PSI.[/b]: [3 Tons X 1.5] - .5 X 2240 = 8,960 psi)
3 1/4 tons = 9,682 psi
3 1/2 tons = 10,427 psi
4 tons = 11,917 psi
Major Sir Gerald Burrard published an estimated LUP Tons/ Sq. Inch (TSI) to piezoelectric transducer Pounds/ Sq. Inch (PSI) conversion formula in the Third edition of The Modern Shotgun, 1955, Vol. 2 p. 277 derived from simultaneous crusher and transducer pressure readings in a test barrel. He also pointed out the under-reporting of pressure by LUP:
“The calibration of lead crushers by means of the piezoelectric gauge suggests that lead crusher pressures are somewhat on the low side; 2 Tons per square inch being about 2.5 with the piezoelectric gauge…”
Estimated Long Tons Per Square Inch Lead Crusher Pressure (Cp) conversion to PSI (pound force per square inch) (Cp x 1.5) - .5 = TSI, TSI X 2240 = PSI
Using this formula: 3 Tons/sq. inch by LUP (crushers) = 8,938 PSI (pounds/ sq. inch) by transducer
3 1/4 Tons = 9,682 psi
3 1/2 Tons = 10,427 psi
3 3/4 Tons = 11,480 psi (The SAAMI maximum for 2 3/4” 12g is 11,500 psi)
4 Tons = 11,917 psi
BUT “Eley Shooter's Diary 2005”: “The later transducer system uplifts the (PSI by LUP) values by approx. 14%.”
Burrard's conversion formula for tons/sq. inch as measured by LUP is probably close to modern piezo transducer measured pounds/sq. inch (psi).
Since we cannot KNOW the conversion for psi as measured by LUP to psi as measured by transducers, adding 10 - 14% to the load pressures reported as psi by LUP seems reasonable.
The Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives standards were not ratified until 1969.
http://www.cip-bobp.org/homologation/en/tdcc_public?page=1&cartridge_type_id=7 12g 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.
SERVICE pressure 740 BAR = 10,733 psi; PROOF 930 BAR = 13,489 psi
Maximum statistical individual pressure 850 BAR = 12,328 psi
12g 76 mm = 3” lead “High performance/superior proof” transducer pressure
Service 1050 BAR = 15,229 psi
Maximum statistical individual pressure 1200 BAR = 17,405 psi
Magnum proof 1320 BAR = 19,145 psi
Both 65 and 70 mm 16g standard is SERVICE 780 BAR or 11,313 psi; Maximum SERVICE 900 BAR or 13,053 psi; PROOF 980 BAR or 14,214 psi.
Both 65 and 70 mm 20g standard is SERVICE 830 BAR or 12,038 psi; Maximum SERVICE 950 BAR or 13,779 psi; PROOF 1040 BAR or 15,084 psi.
The British joined CIP in 1980 but the Proof House did not make CIP standards uniform until 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, 2 1/2” chambered 12g guns were usually proofed at 850 BAR (the old 3 TONS/ sq. inch). 2 3/4” chambered may be proofed 900 BAR (old 3 1/4 TONS) or higher.
And in parting please remember Proverbs 1:32 (revdocdrew non-inspired version)
“The waywardness of the simple will kill them, and the complacency of fools will destroy them (and their barrels).”
Joined: 12 Mar 2005
Good to hear from you. Where ya been? How ya been? Hope all is well with you.
Being an expert on simple because I am, I'm a firm believer in K.I.S.S. Been working for me for decades.
As for complacency, I agree. Complacency is what causes fools to let their guns go to rust. Rust is insidious, and it never sleeps. Rust destroys guns every time when we turn our backs on it. I think neglect is the biggest danger when it comes to old guns. Just sayin'.
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