John: A DuPont Ballistic Table was published in Parker Brothers' “The Small Bore Shotgun”
c. 1920 http://parkerguns.org/pages/PDF%20Do...%20Shotgun.pdf
It is clear that this table converts Long Tons to PSI simply by multiplying by 2240; NOT using Burrard’s conversion
p. 7 “All powders referred to on these pages are of the bulk nitro"
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
DENSE Smokeless Powder pressures would be 1000 - 1,500 psi higher
The 1933 edition of “Smokeless Shotgun Powders” by Wallace Coxe, ballistic engineer of the Burnside Laboratory of the E.I. du Pont de Nemours & Co. reported the pressure for 1 1/4 oz. 3 Dr. Eq. of DuPont Bulk Smokeless at 9,600 psi by LUP.
Of course everything changed with Western's boomers
In a 1927 Western Cartridge Co. flyer “Super-X The Long Range Load” by Capt. Chas. Askins the 12g “Duck Load” (not specified but presumed to be 1 1/4 oz. Super-X “Field”) is described as 3 1/2 dram (38.5 gr. DuPont Oval Powder = 11 gr. / Dr. Eq.); at 1400 fps (at the muzzle rather than 3 feet) and 1000 fps average over 40 yards, with a breech pressure of 3 3/4 tons or about
11,480 psi by Burrard’s conversion.
3” Super-X “Record” with 1 3/8 oz. at MV 1400 fps with 4.25 Tons psi =
13,160 psi
Super-X 10g 1 5/8 oz “about 4 1/2 Drams” No. 2 shot Full choke 32” barrel, average velocity over 40 yds. 1030 fps; “up to 13,000 psi” by crushers = about
14,500 psi by modern transducers.
Super-X 3 1/2” 10 Gauge Magnum in Ithaca Gun Co. with bore .795” with 2 oz. shot; pressures “about 5 Tons” =
15,680 psi
Threaded Mode