From the 1928 edition of “Smokeless Shotgun Powders” by Wallace Coxe
"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."
Coxe reported 3 1/2 Dram Eq. 1 1/4 oz. load (1275 fps) pressures, measured by crushers (LUP) and expressed as psi:
DuPont Bulk smokeless powder - 11,700 psi
Schultze Bulk smokeless powder - 11,800 psi
28 grains of Ballistite Dense smokeless powder - 12,600 psi
40 grains of DuPont Oval Progressive Burning powder - 9,400 psi
I think these are the best period numbers available, recognizing that modern piezo numbers would be 10-14% higher.
If we divide 11,700 by 2240 we get 5.2 tons which would fit the 1933 lawsuit numbers:
The “maximum commercial load” was described at “11,200 psi (divided by 2240) = 5 long tons”.
“Highest Mean Service Pressure” equivalent PSI transducer values as converted from LUP by Burrard’s formula (Cp x 1.5) - .5 = TSI, TSI X 2240 = PSI:
2 tons/sq. inch (NOT 2 X 2240) = 5,600 psi (pounds/sq. inch) = 386 BAR
2 1/2 tons = 7,280 psi = 502 BAR
3 tons = 8,960 psi = 618 BAR
3 1/4 tons = 9,800 psi = 676 BAR
3 1/2 tons = 10,640 psi = 734 BAR
3 3/4 tons = 11,480 psi = 792 BAR
4 tons = 12,320 psi = 850 BAR
Tons to psi by piezo transducers conversion provided by the Birmingham Proof House 11-2001 (courtesy of Larry Brown) are very close to Burrard's
2 1/2” / 3 tons = 8,938 psi
2 3/4” / 3 1/4 tons = 9,682 psi
3” / 3 1/2 tons = 10,427 psi
3” / 4 tons = 11,917 psi
I think Coxe was simply doing a formula conversion long tons/sq. inch to PSI using 2240. They were not using piezo transducers to measure psi in the 30s.
|
Hybrid Mode