There are two different kinds of GI Bore Cleaner. The older type is a clear, dark brown and smells (strongly) of creosote. The newer type is a milky light brown color and smells bad too. Both contain water and will freeze, as our GIs found out in the Battle of the Bulge. They will prevent rusting due corrosive salts (pottasium chloride) in the bore from corrosive primers. After cleaning, bores need a coat of oil so they won't rust from humidity in the air. Bore cleaner comes in various size containers; I've used the one quart cans to clean the bores of 105mm howitzers.