In a 1927 Western Cartridge Co. flyer "Super-X The Long Range Load" by Capt. Chas. Askins the 12g duck load is described as 38 1/2 grains or 3 1/2 dram (powder not specified but likely DuPont Oval) with a breech pressure of 3 3/4 tons or 11,480 psi.
Using the 2240 lb long ton 3 3/4 tons comes to 8400 lbs. Anyone want to explain where those extra 3,000 lbs came from when the pressure was given in PSI. It is also noted if you use the formula worked out by the British for converting crusher tons to PSI 3 3/4 tons converts to 11,480PSI. This formula was sated to not be "Exact" but close enough for a safe comparison. If that 1927 "Conversion" of tons to psi was merely a wild guess someone sure was doing some good guessing. Also "IF" all those loads stated from this era with pressures in the 11K+ range were in fact actual Crusher Pressures our ancestors weren't shooting shotshells through their old guns, they were shooting Hand Grenades. 5 tons = 11,200 lbs. 5 tons in crusher pressure would translate to something around 15˝K PSI.
I do completely agree that in older data crusher pressures were very often stated simply as PSI so care has to be used in their interpretations.
I will also state the shells developed such as the "Super X" using more progressive burning powders did not raise pressures over the current heaviest available loadings. What they did was allow heavier shot charges, higher velocities (Or Both) while staying within an accepted max pressure level.
Compare these loads posted by Drew & note that all these loads are recommended in a 1913 Lefever Arms Co catalog as "Proper" in their 12 ga guns of over 7 lbs weight, except the one using Oval which of course was not then available
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Coxe previously reported 3 1/2 Dram Eq. 1 1/4 oz. loads:
DuPont Bulk smokeless powder - 11,700 psi
Schultze Bulk smokeless powder - 11,800 psi
28 grains of Ballistite - 12,600 psi
40 grains of DuPont Oval Progressive Burning powder - 9,400 psi
