I live in Seward, Alaska. We are classified as a rainforest. A maritime rainforest at that. Needless to say its wet... Always.
I usually carry a .44 magnum with a small holster for easy packing, it doesn't cover much of the gun. Gun gets wet and stays wet, so do the slugs in the chamber.
There are times where the rounds in that gun will go months like that, get wet, end of whatever trip I wipe them dry, dry and oil the gun, put them right back in. Never have I ever had one of my .44 mag loads misfire, or quib, even after getting repeatedly wet. I've never used any sealant on any load.
You are using a primer that the cup seals enough to hold in 25000-60000 psi depending on your caliber. And a bullet that is seated strong enough the recoil from the previous load won't move it. To think moisture could get in past all of that is silly.