Geez, these threads go on and on....
There wasn't any Hodgdon "H4350" until the 1990s, and the original 4350, developed by what was then DuPont as IMR (Improved Military Rifle) was officially introduced for public sale in 1940--though according to Phil Sharpe's classic book Complete Guide to Handloading could be purchased in 1939 by personally appearing at the DuPont factory in Delaware. (Imagine that happening today!) It wasn't developed for anything other than sporting cartridges, but probably led to the original H4831, the somewhat slower-burning 20mm cannon powder Bruce Hodgdon started selling after the war.
I still have some of the original H4831 mil-surp powder, both in paper bags and in a waxed-cardboard canister, and it still works about like it supposedly did when Hodgdon first started selling it. Burned a BUNCH of it over the years, partly because it was widely available when I started handloading a long time ago, and partly because an older gun-writer friend (even older than I am now!) still had about 10 pounds left when he quit handloading in the 1980s--and gave it to me.
But the original mil-surp powder varied somewhat from lot to lot--and unlike today's powders for handloaders, was NOT blended with other lots so the burn-rate would be more consistent. Know this from testing various batches over the decades.
