You bring back memories. Yes, I have used lots of that stuff. We used to group buy it in 50 pound kegs for just over $20. in the early 60s. Yes, it is WW2 surplus. But, here is a little known fact. After WW1 the Americans had huge amounts of powder left over. They got it into monstrous sized solid masses and sunk it in water. They revived it in WW2 and used it. Thus, it is possible that our old surplus H4831 may have come from WW1!
I will throw in something else here about wartime explosives, while I am at it. Mercury is used in making explosives, like bombs. The entire supply of mercury for all the allied forces in WW2, came from a mine in northern BC. If anyone wants to know, I will give particulars.
I still have some of the war surplus H4831 and won't hesitate to use it. I don't have a chronograph now, so waiting to test it until I can chrono it.