Re: Powder shelf life?
I recently reworked nearly 200 rounds of reloaded M855 ammo I bought at a Dallas gun show 20 years. ago. Each round had numerous problems, at least 3 problems each and a few rounds as many as 5 problems. Several of them had wet clumped gunpowder in them where the reloader did not properly dry his cases thoroughly. I blended all the powder together and let it sit for a while. I backed off the loads by .3 grains and reloaded. It was some of the most accurate M855 that I have tested so far. Now, if you haven't let the powder sit in a wet case for the past 20 years, it should be no worse for wear than mine was.
Guys have thrown smokeless powder in water overnight, dried it out and reloaded it and it shot just fine. Don't try this with blackpowder. Smokeless powder is supposed to have a 30-50% moisture content. Drying it completely out with dessicant would be a mistake, and that's probably one reason that rounds that have set around in the hot sun for a long time develop dangerous pressures.