I don't load mine the day before, but I sometimes leave it out in the truck or in an unheated building overnight after removing the capwith the load still in the barrel.

Your problem mayhave been caused by condensation in the bore due to being taken from a warm room out into the cold, but this is unlikely! Condensation usually forms when you take a COLDgun inside into a warm, moist room, not vice-versa! That's why I leaveloaded ones out in the cold until the hunt is over.

I have hunted 7 days straight in wet weather in the Adirondacks with the same load in my gun, but I had a piece of plastic wrap over the muzzle and also around the lock and nipple portion. At the end of the 7 day hunt (no shot!), I fired it at a target, and it was still right on. That was with Clean Shot (American Pioneer) powder, which is worse than even BP for moisture problems. IF I am able to hunt more than one day, I usually leave the loaded but unprimed gun out in the cold overnight. If the hunt is over, I have found that it is just as easy to shoot the round out then clean at home at the end of the day, since if you draw the charge with a ball puller, you still have some bore cleaning to do because some of the powder always seems to remain in the bore anyway.