Bulk Smokeless ("E.C.", "Schultze", and DuPont) were introduced in the U.S. c. 1892, and were in general use by 1895.
The Parker Brothers
1893 Catalogue stated:
“Our guns are bored on the latest improved system for shooting Nitros, or Smokeless Powder, and all our guns are tested with some one of the most approved makes, and a tag accompanies each gun, giving the results of such a (pattern) test.”
A DuPont Ballistic Table was published in Parker Brothers' “The Small Bore Shotgun” c. 1920
http://parkerguns.org/pages/PDF%20Do...%20Shotgun.pdf
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
More here
https://docs.google.com/document/d/1...UOZEFU/preview