Yes i know black powder what was used back then would rust your gun because the residue and/or unburnt powder would attract moisture. Then there was Mercury primers which mercury would attract moisture not the powder residure and/or unburnt powder. It was the Mercury from the primers that would attract the moisture not the powder and or residure or unburnt powder right? I hear of ammo from the 1950's being the type that would rust your gun. I only hear of black powder being used by musket enthusiasts, civil war renactors and experimental firearms. But Today's smokeless powder that is used in todays cartridges will not attract moisture no matter what even if the gun has not been cleaned. So you could leave a gun dirty forever and it would never rust right??? Also nobody uses Mercury Primers anymore right? Just wondering i actually do a 100% take down ( Not Just a Field Strip ) of all my guns after every single time i shoot them. I Know that is a little to over obsessive unecessary for any firearm.