I have a Ruger Old Army pistol that I left loaded for several years. When I did discharge the arm and cleaned the weapon I found all cylinder chambers where pitted. Not pitted to a dangerous degree or making the pistol unusable but it chaps my butt none the less.

We all know that black powder residue is hygroscopic but I had not realized unfired black powder is hygroscopic also.

If you don't have a need to keep the firearm loaded then unload it and clean it.

Vlad