The Explosives Company of Stowmarket, England introduced E.C. (made from cotton) in 1882.

The American E.C. & Schultze Powder Company was established in Oakland, New Jersey in 1890.
E.C. No. 1, New Schultze, and New E.C. No. 2 were advertised by the company in 1902, which was purchased by DuPont in 1903.

c. 1893 William Read & Sons, Boston advertisement
Regulated for 45 to 48 grains (3 1/4 - 3 1/2 Dr. Eq.) Schultze or similar Nitro powders, and 1 1/4 oz. Shot.



The Overland Monthly, Oct. 1895 Smokeless Powder For Shotguns
http://books.google.com/books?id=Wv0MAQAAIAAJ&pg=PA446&lpg
on p. 453
3 1/4 Dram Eq./40 grains DuPont Bulk Smokeless 1 1/8 oz. (1255 fps) = 7440 psi
3 1/4 Dram Eq./44 grains E.C. Bulk Smokeless 1 1/8 oz. = 7584 psi
+ 10-14% for modern piezo transducer numbers

The heaviest pre-WWI Smokeless loads would have been 1 1/4 oz. 3 3/4 Dr. Eq. with Schultze Bulk Smokeless at about 14,000 psi; "E.C." about 14,750 psi ; and with Ballistite Dense Smokeless about 15,250 psi.
At the 1901 GAH at Live Birds Harold Money was using a Parker with 1 1/4 oz. shot and 52 1/2 gr. E.C. = 3 3/4 Dr. Eq. = 1330 fps
http://library.la84.org/SportsLibrary/SportingLife/1901/VOL_37_NO_03/SL3703012.pdf
In an 8# gun that would be 29 ft/lbs of free recoil

Boomers indeed.

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