ORIGINAL: Mastevt
Can anyone tell me if pyrodex goes bad after a year? like if it absorbs moisture from the air, I stored my pyrodex last year in a ziplock bag just to be safe, but does it also have a shelf life where it wouldn't be any good even if I stored it this way?
Yes, Pyrodex in any form will absorb moisture, if it is not kept in a sealed container of some sort. The plastic jugs the loose powder comes in have an adequate lid, if it is screwed on tight. As to the pellets, I recommend keeping them in their factory box and put the box in one of those steel air-tight GI .50 caliber ammo cans you can buy from Cabela's, Cheaper-Than-Dirt, etc.
The actual length of time the powder will last depends on how well sealed the container is that you keep it in. I have several old containers of Pyrodex powder, and it still fires. I have not chronographed it in the last several years, so cannot say if it has lost any strength or not.