In the Western Cartridge Co. Super-X booklets of the 1920s and early 1930s Capt. Chas. Askins states the velocity of the 3-inch Super-X is a bit over 1000 fps over forty yards. The 1941 Winchester Ammunition Guide gives the velocity over forty yards for the 12-gauge, 3-inch, Super-Speed, 1 5/8-ounce load as 965 fps.
Another shotshells ballistics chart I have shows the muzzle velocity for the 1 3/8-ounce load as 1295 fps and the 1 5/8-once load as 1200 fps. I have no attribution for this chart.
As for pressure they would be withing SAAMI Specs.
Actually, the answer is likely zero and zero. Those pre-war non-corrosive primers have likely exceeded their useful life.
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