Two months ago, I took a co-worker from California to the local shooting range. He really enjoyed shooting my MP5 and MP5K SBRs. Near the end, he was complaining about sweaty hands (he came from Walmart loaded down with 800 rounds of ammo). Lo and behold, my mags now have rust spots on them. Unfortunately, he handled about a dozen of my 30 round mags at the range. Any tips on how to treat the mags and prevent the rust from spreading? At least I don't have to worry about my UMP 9mm mags!