Getting a new bright and smooth finish on a rusty octagon barrel is not difficult at all. The process isn't complicated, though it is time consuming and may take a few hours.

Here's one I just finished working. Fortunately, the bore is bright and shiny. But the outside had moderate rust and some shallow pitting.





BEFOREFORE


Here's how it looked after two hours of work.



AFTER


The work was done with a 12" mill file.



The trick is to keep the file flat to the barrel and make long smooth strokes.

A good technique is to make a stroke about a foot long. Then lift the file, turn it sideways, and tap the edge on a piece of wood to knock out any chips. Use a file card to brush out any chips that do not fall free.

Do not apply a lot of pressure - think along the lines of the pressure you would use to apply suntan lotion to Scarlett Johansson's back.





For an extra smooth finish have a seat in a comfortable chair and repeat the process with a finer 6" or 8" mill file.



If you want it really shiny, follow that by wrapping the file with 400 grit Emery paper and have at it.