Helps too to seal the pan, so whatever moisture gets to the lock area is cut off there. Two ways I've done this: one, BEFORE loading, warm the underside of your frizzen and the edges of your pan, and apply wax of some sort where the frizzen seals to the pan; two, which will work better in the field, load up in as dry a place as you can find, and apply grease along the pan's edges, then prime and close your frizzen. Both methods provide a decent seal against moisture. Obviously, all bets are off after the first shot.