ORIGINAL: cayugad
Well I have had "open" powder and pellet around the house for over a year and it shot fine. I had some Clean Shot that was over four years old and it shot fine. I think a lot has to do with how you store it between use. I keep it in the original container when ever possible. I make sure the powder caps are on straight and tight. Also I store the powder in a cool dry place. So far so good. I usually buy my powder by the case and some of it will sit around the house for some extended times...
What he said! Storage conditions are the determining factor. I suppose the info in your book has some validity, IN A WET CLIMATE, and some powders are worse than others! Looking at those little plastic boxes that Pyrodex pellets come in, I can't believe they are moisture proof! After opening one, I'd store it in a good sealed GI .50 cal. ammo box. But I don't use pellets, just canistered powders, and if you keep the lids on real tight between range trips, the powder will remainOK.
Any true black powder that is dry enough to pour freely will be just as strong as ever. It is some of the the substitute powders that seem to absorb enough moisture from a humid atmosphere to lose some strength.Just keep them
ALL stored in a dry environment!
This stuff, mixed with your loose powders, seems to keep them dry. I use it in my flinlock priming pan powder.
Dry Pan, by RMC, waterproofs blackpowder, makes dry flys float.
#ML002 14oz Price $3.95