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Sidelock
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What SGJ said

From the 1928 edition of “Smokeless Shotgun Powders” by Wallace Coxe, ballistic engineer of the Burnside Laboratory of the E.I. du Pont de Nemours & Co. “DuPont Oval can be loaded with 1 3/8 ounces of shot in a 12-gauge shotgun to develop the same velocity and pressure as obtained with a load of 3 1/2 drams of DuPont Bulk Smokeless Powder or 28 grains of Ballistite and 1 1/4 ounces of shot. The relation naturally holds with other charges, but as DuPont Oval is used principally for maximum loads the comparison is more striking as it shows the possibility of using a heavy load with DuPont Oval that would be an abnormal load were it used with DuPont Bulk Smokeless, Ballistite, or other existing old-style types of shotgun powders.”
Coxe reported 3 1/2 Dram Eq. 1 1/4 oz. loads (the standard c. 1900 Live Bird load):
NOTE: pressures were measured by crushers (LUP) and modern transducer measurement pressures would be 10 – 14% higher
DuPont Bulk smokeless powder - 11,700 psi
Schultze Bulk smokeless powder - 11,800 psi
28 grains of Ballistite Dense smokeless powder - 12,600 psi
Note all 3 are greater than the SAAMI 12g 2 3/4” recommended maximum pressure of 11,500 psi.
40 grains of DuPont Oval Progressive Burning powder - 9,400 psi

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Sidelock
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Originally Posted by Drew Hause
Fortunately we have numbers to prove that ed is incorrect.

DuPont Ballistic Table that was published in Parker Brothers' “The Small Bore Shotgun” c. 1920
http://parkerguns.org/pages/PDF%20Documents/Small%20Bore%20Shotgun.pdf
It is clear that this table converts Long Tons to PSI simply by multiplying by 2240; NOT using Burrard’s conversion
“All powders referred to on these pages are of the bulk nitro kind ranging from 12 (“New Schultze”, New “E.C. Improved No. 2”) to 13 1/3 (original DuPont Bulk) grains per dram…”
DuPont Bulk was introduced in 1893
"New Schultze" and "E.C. Improved" in 1903
Dense Smokeless powder pressures were higher. "Infallible" was introduced by Laflin & Rand in 1900

[Linked Image from photos.smugmug.com]

Numbers require adding 10 - 14% for modern piezo transducer pressures.
12 gauge
3 Dr. Eq. 1 1/8 oz. = 8,110 psi
3 1/4 Dr. Eq. 1 1/8 oz. = 8,960 psi
3 1/2 Dr. Eq. 1 1/4 oz. = 9,900 psi
16 gauge
2 3/4 Dr. Eq. 7/8 oz. = 7,035 psi
3 Dr. Eq. 1 oz. = 8,980 psi
20 gauge
2 1/2 Dr. Eq. 7/8 oz. = 12,655 psi

Very similar to modern pressures when adding 10-14%, and the 20g far exceeds the SAAMI recommended max. of 11,500 psi

If ed has post-WWI pressure data documenting higher pressures he is invited to post the information.

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Very similar to modern pressures when adding 10-14%, and the 20g far exceeds the SAAMI recommended max. of 11,500 psi

[/quote]
As usual, Doc Drew, excellent historical information. However, you slipped on the current SAAMI recommended max pressure. Current max avg pressure figure for the 20ga is 12,000 psi. So the vintage loads were actually higher than the current standard . . . but not by quite as much as you indicated..

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I had a 1912 20ga flues in otherwise 95+% condition that had 2-15/16” chambers. Also a 30” 20ga flues with 2-15/16” chambers, but it’s condition was much lower and I can’t be as sure it wasn't modified. I know of one other very high grade 20ga flues with almost 3” chambers.

Also, the high condition gun had a “2nd” marked on the barrel lug with no obvious variation from a standard gun other than the chamber length.

Last edited by bsteele; 09/14/21 05:29 PM.
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