RE: Storing Muzzleloader
While I know many who leave them charged for days on end,I agree with the others why chance it. I dump the load unless subjected to moisture in which caseI will fire it off prior to days end (if nothing else it provides you with a baseline how your ML and powder fair in moist conditions), this way I save the bullet at least for the range. MyMLs are then swabbed, re-oiled, dry patched to remove excess oiland then re-charged the following morning before leaving the house.
As far as weatherproofing the barrel I have always taped the muzzle end of the barrel on my rifles (ML's and CF's) with electrical tape. It is cheap, easy to find, safe, does not affect the POI and does the job.