ribs

[charlie cleveland]

wow.... lot s of crude under those barrels...i ain t got the nerve to look under some of my old guns...charlie

[John Truitt]

what is the main source for such a build up of rust? esp is the ribs are not loose with any signs of separation etc.
is it moisture over time/ lubricants/ etc?
Do we see this with modern ribs relaying?

Just trying to future my knowledge.