DEHUMIDIFIER in the room the guns are in!!!! IMO take them from the case (if they are in cases) and open up the actions and put them somewhere they can get some air....

i had that problem...DAMP basement bedroom, humid summer, and cases under the bed.....dehumidifier and opened all the actions and put them in all the corners of my room....not a great idea if any unauthorized personell(kids, kids friends over when your not home, blah blah blah) might be around....

but in my case i was the only one in the room so i was fine...humidity is a killer....im freaking out now im away all summer and dont know how the new house handles the humidity...im hoping well...central AC and all the guns are upstares now.....