If you can't find it. Here it is again.
Modern black powder substitutes have come a long ways since Dan Pawlak, of Issiquah, Washington first formulated the earliest form of Pyrodex back in the early to mid 1970s. During the late 1980s, I conducted a "shelf life" test with Pyrodex "RS"...and in the course of 6 months, from October 1 to April 1, I found that a 100 grain charge of the powder, behind a saboted 260-grain Speer .451" JHP lost more than 100 f.p.s. (shot from a 24" barreled Knight MK-85). And by the end of that summer, velocity was down nearly 300 f.p.s. from the velocities I had gotten when I first shot out of that canister of powder a year earlier. And that was a very common complaint with Pyrodex. Once the seal was broken, the powder lost its oomph. Powder used one season could not be used the following season...Toby Bridges