Click on the link to the high-res photo, and you'll change your mind. The brass and the copper(?) jackets on the bullets have that distinctive blue corrosion on them.
The gun itself looks pretty beat up, too.
blue or green corrosion is typical on copper and brass, especially if its been exposed to salt water. The rust I was refering to appears to be rust dust that came off the beltand was left on the casing