I was told that "heat" is bad for storing powder - like in an uninsulated garden shed where it gets way hot in summer. Somewhere on Internet says that room temperature should be good - as you allow storage to get warmer than that, the powder break down starts. So far as I know, that "break down" is NOT reversible - you can not "fix" it, if it happens. I never read similar about primers - I have no idea if heat hurts them like it does powder. I do not have anything near as old as previously posted - most of my primers and powder were bought within previous 10 years - no complaints about either, so far.
Some years ago, I seem to recall some powders coming in metal tins (IMR?), or perhaps just metal ends on cardboard bodies (Hercules?) - I suspect that good cold could also cause condensation on inside of those metal surfaces - metal would rust, and no doubt that moisture not doing the powder any good. I have read in various emails and posts on CGN about people choosing to toss 8 pound jugs of powder because it "turned" - all describe a distinct acrid smell - not "normal" - when the powder jug is opened. I do not recall anyone describing how they decided to toss primers, though - I do not know how to "check" them, except for visual external condition - which could be easily misleading ...
