#2400 powder was introduced by Hercules in 1933 as a replacement for their old SR80 (Sporting rifle). It was at that time used for small capacity rifles such as the Hornet & .218 Bee. That was it's purpose of introduction, so it "WAS" in fact a fast rifle powder. Elmer Keith soon began to use it for heavy .44 special revolver loads. A Lyman handbook dated 1950 shows loads for the .410 of Hercules "Red Dot", "Infallible" & "Herco" and Dupont "Oval" (No 2400 loads are given at this time). By the late 50's they listed loads only for 2400 but nothing lighter than ½oz & this became the standard powder for loading both ½ & 3/4oz .410 loads for a number of years. I believe though, it would be "Entirely Accurate" to say the "Classical .410" was loaded with from 5/16-3/8oz of shot & with regular shotgun propellants. The use of the fast rifle powders such as Hercules 2400 & Dupont 4227 came later with it's Magnumization. The only thing that might even allow a powder as slow as 2400 to even work with a charge as light as 3/8oz is the fact the charge would be so small it could obtain complete ignition from the primer designed to light a full 12ga charge. Otherwise it likely would "Fizzle".
