OK, I suppose I'm going to ruffle a few more feathers, but just how is moisture supposed to get to the powder charge? Moisture collecting on the outside of the metal will have no effect on what's going on inside the barrel! The powder is sealed by the bullet and sabot, or patch, or whatever, at one end, and by the cap at the other. Some folks go as far as to seal the cap with bullet lube. A flintlock can be sealed at the flashhole with a toothpick, which also serves as a "loaded gun" indicator.

Whatever moisture is in the powder can't get out, nor can any more get in.

OldBob