Some additional data on American shotshell pressure measurement: Charles Askins reporting in 1929 on tests at DuPont's Brandywine Laboratory of the 12-gauge/3-inch load with a max charge of its Oval progressive burning powder, as "taken from a DuPont ballistic sheet":
37 grains Oval, 1-3/8 ounces of No. 6-shot ------> 4.50 tons per square inch
Now then, 4.50 X 2200 X 1.15 = 11,385 psi as converted to approx. modern transducer reading
Or, if you prefer, 4.50 X 2240 X 1.15 = 11,592 psi as converted
Right on par with the current SAAMI max mean pressure for 12-gauge/3-inch at 11,500 psi.
In net, I continue to believe that "Burrard's Conversion" doesn't apply to pressures of American factory shotshells and thus the guns designed for them.
Last edited by Frank Srebro; 01-23-2017 at 07:45 PM..
Reason: Added summary
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