It does appear that Coxe was simply converting tons X 2240 to derive psi.
From “Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics”,
1927, a DuPont Oval Pamphlet, p.20.
Dram Eq. is listed on the graph as 3; charge was 1 1/4 oz. Pressure is expressed in Long Tons.
Using Burrard’s estimated Tons Lead Crusher Pressure (Cp) conversion to PSI (pound force per square inch): (Cp x 1.5) - .5 = TSI; TSI X 2240 = PSI
in BLACK
IF Coxe was simply converting Tons X 2240 to estimate the PSI in
BLUE and is compatible with other 3 Dr. Eq. published measurements (+
10-14% for modern transducer numbers)
Ballistite maximum pressure at 1” was 4.9 Long Tons = 15,344 psi (by Burrard) or
10,976 psi
Schultze at 1 3/4” was 4.5 Long Tons = 14,000 psi or
10,080
DuPont Bulk at 1 2/3” was 4.1 Long Tons = 12,656 psi or
9,184
FFFg at 1 1/2” was 3.8 Long Tons = 11,648 psi or
8,512
DuPont Oval at 2” was 3.5 Long Tons = 10,640 psi or
7,840
I wish he'd just used the Tarage table for psi instead
Or maybe he did, and for some unfortunate reason chose to express the numbers as Long Tons??
The
BLUE psi numbers are similar to “Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics”,
1933. The pressure curves (PSI by LUP) are also for a 3 Dr. Eq. 1 1/4 oz. load (+ 10-14%)
DuPont MX = 9,800 psi
DuPont Bulk = 9,600 psi
FFFg = 9,000 psi
DuPont Oval = 8,700 psi