Originally Posted by Mercator
Acetic acid is mildly corrosive to iron. It forms rust in the first place. Whether it chemically dissolves rust at the same time, I don't know, but the choice seems odd. Rust is not chemically aggressive, and requires really strong solvents. It is best removed mechanically, steel wool and such. (Another post that won't make me friends...)
Please allow me to clarify.
I use vinegar, as well as other solvents, separately,
in order to "shock" dirt and corrosives from the inside of a
dirty barrel. I cannot advise anything be used on the outside
finish of your gun, except what the manufacturer advises.
Afterward, it is always wise to use solvent to break up and
remove the vinegar, ammonia, etc. Then OIL the barrel lightly.
UNDER NO CIRCUMSTANCES should you leave any chemical or
solvent in your barrel, after you are done cleaning, and oiling it.