Clean it ASAP. Hot, soapy water works best, but any water is useful. I usually will use soapy water like solvent and patch it through the bore to help dislodge all the crap. Clean anywhere that gets gas flow - clean the chamber and around it and the bolt face. When I lived in a humid area (San Francisco area), I would shoot a ten round string then pull the bolt immediately. The barrel would be warm, so it would heat the water up for me. That's a decent way to clean at the range so you don't have to wait until you get home. You won't have problems with corrosion if you do it like that.
Heck, I thought everyone knew how to dispose of power. All it takes in one match......disposal of powder...