I just (finally) upgraded my endoscope and looked inside the slide of my 1947 Olds Standard. I no longer believe that the inners are replacements.

There is a LOT of surface corrosion, and a lot of deposits. I had, of course, cleaned it a number of times already. So "normal" cleaning hasn't done the trick. I'm thinking I need to approach it in the same way as cleaning the outer, plus a lot more brushing (probably with appropriately sized gun barrel brushes -- .45 or .50 cal. should work), maybe with a low-speed electric drill to drive it rotationally. As I think of going the vinegar-soak or citric cleaner route, I'm wondering if CLR might be a better approach. It works especially well on calcium deposits.
Thoughts and experience?