Maj. Sir Gerald Burrard, The Modern Shotgun, 1955, Vol. II, “The Cartridge”, Appendix VI, p. 284
Webley Pendulum Gun. Taper from cone to barrel bore .735” to .733” over 12”; .733” bore to choke .690”
Pressure converted using Burrard’s estimated Long Tons/ Sq. Inch Lead Crusher Pressure (Cp) to PSI (pound-force per square inch):
(Cp x 1.5) - .5 = TSI, TSI X 2240 = PSI.
…………………..............……………………………….…1 inch………6 inches….%
“E.C.” No. 3 3 Dr.Eq. 1 1/16 oz. shot…………...7,750……….3,786……49
“Schultze” 3 Dr.Eq. 1 1/16 oz. shot…….…….….6,842……….4,323……63
Smokeless Diamond 3 Dr.Eq. 1 1/16 oz.shot….8,758……….3,685……42
Smokeless Diamond 3 Dr.Eq. 1 oz. shot……..….8,355……….4,021……48
Sporting Ballistite 3 Dr.Eq. 1 1/16 oz. shot…..9,901……….4,088….…41
Preacher, in this shotgun barrel pressure data for long obsolete powders, we see two 3 Dram Equiv. loads for Smokeless Diamond powder.
It seems odd that there is claimed to be a greater pressure drop at 6" for the heavier 1 1/16 oz. shot load than the lighter 1 oz. load with the same powder charge. Did you notice that, and do you have an explanation? The disparity seems to be greater than a normal Standard Deviation for equal loads, let alone equal powder loads with different shot weights.
