Possibly an engineer would like to tackle the evolution of measuring shot velocity.
By 1900 "muzzle velocity" was reported, but even into the 20s "average velocity over 120 feet" was also reported.
This is a DuPont Ballistic Table published in Parker Brothers' “The Small Bore Shotgun” c. 1920
http://parkerguns.org/pages/PDF%20Documents/Small%20Bore%20Shotgun.pdf It is clear that this table converts Long Tons to PSI simply by multiplying by 2240; NOT using Burrard’s conversion
p. 7 “All powders referred to on these pages are of the bulk nitro kind ranging from 12 (“New Schultze”, New “E.C. Improved No. 2”) to 13 1/3 (original DuPont Bulk) grains per dram…”
Original “E.C.” and “Schultze” were 14 grains/dram
In a 1927 Western Cartridge Co. flyer “Super-X The Long Range Load” by Capt. Chas. Askins the 12g “Duck Load” (not specified but presumed to be 1 1/4 oz. Super-X “Field”) is described as 3 1/2 dram DuPont Oval Powder; at 1400 fps (at the muzzle rather than 3 feet) and 1000 fps average over 40 yards.
And modern "muzzle velocity" is measured 3 feet from the muzzle so older MV Dr.Eq. numbers are different.
Anyway: A 1 oz. 12g 2 3/4 Dr.Eq. load is 1145 fps. A 1 oz. 20g 2 3/4 Dr.Eq. is 1220 fps because the ejecta is faster through a smaller tube according to that Bernoulli fella
