an ultra-sonic cleaner will do wonders for the action. Once it comes out of the ultra-sonic any remaining rust will be soft and can be cut away with a sharpened piece of brass. You could just boil the barrels and convert the red/brown rust to black and card. Once converted to black oxide it is stable and will not rust further. Best of luck with it.
Steve

www.bertramandco.com ACGG Pro
Pope Leo is my war hero
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