RE: WD 40as gun oil?
It will work really well for cleaning and inhibiting rust, but the downsides outweigh the positives. Its false economy to save a few dollars instead of using something made for guns. If you insist on being cheap, use Mobil-1 synthetic oil- but then again a quart of this stuff will cost as much as a can of Sheath, CLP, or RemOil anyhow.