does vinegar evaporate quickly? Just wondering if it has to have a lid?
A friend of mine found an old rifle (something weird like a 26-40 or something) and everything is rusted solid, I was thinking he could take the stock off and put the barrel and action in a 3" diameter or so metal tube with a bottom welded on it, fill it with vinegar and let it sit for a few days, might work.
as far as brass, idk what vinegar will do to it, but I read on the hamb that it can be really bad for aluminum if it is left to soak.