I love to buy used Kimbers with discolored barrels. I just throw them in my blast cabinet and hit the barrel with glass beads at about 60psi and give them a nice matte finish. I have even run a couple over a felt polishing wheel and they cleaned up nicely. I have gotten some really good deals on these defective kimbers. I have found the best way to avoid future "rust" is to apply a nice thin even coat of oil.