A Winchester Factory Memorandum dated February 6, 1900
12g 2 5/8" Leader with 1 oz. shot
40 gr. DuPont Bulk = 3 1/4 Dr. Eq. = 2.7 tons/sq. inch = 7952 psi (using Burrard's conversion formula)
42 gr. Laflin & Rand Bulk = 3 1/2 Dr. Eq. = 3.3 tons = 9968 psi
12g 2 5/8" Leader with 1 1/8 oz. shot
40 gr. DuPont Bulk = 3 1/4 Dr. Eq. = 3.9 tons =
11,984 psi
G.T. Teasdale-Buckell,
Experts on Guns and Shooting, 1900
https://books.google.com/books?id=P7UrAAAAYAAJ&pg=PA2351 1/8 oz. load comparisons. Pressure converted used Burrard’s formula
42 gr. = 3 Dram Bulk Nitro – 1” chamber pressure 7,920 psi / MV 1208 fps
45 1/2 gr. = 3 1/4 Dram – 9,730 psi / MV 1,274
49 gr. = 3 1/2 Dram – 11,780 psi / 1,328 fps
“The Long 20 Bore Cartridge”,
The Field in
Forest & Stream, October 17, 1908
https://books.google.com/books?id=ejQevDPMUIYC&pg=PA630 2 3/4” case with “Schultze” Bulk Smokeless (42 gr = 3 Dr. Eq.)
The standard 2 1/2” case was loaded with 33 gr. “Schultze” = 2.36 Dr. Eq. (about 2 3/8) with 13/16 oz. shot.
U.S. 7/8 oz. 2 1/2 Dr. Eq. BULK Smokeless pressures were 8000-9000 psi.
36 gr. = 2.57 Dr. Eq. with 15/16 oz. = 4.65 tons =
14,504 psi (using Burrard’s formula) / 20 yd. velocity 1000 fps
37 gr. = 2.64 Dr. Eq. with 7/8 oz. = 4.54 tons = 14,134 psi / 1040 fps
35 gr. = 2.5 Dr. Eq. with 13/16 oz. = 3.45 tons = 10,472 psi / 1068 fps