http://www.brownells.com/aspx/NS/GunTech/NewsletterArchive.aspx?p=0&t=1&i=503

Fellow posted a link for this over on MoWhitetails and I thought it was very interesting.

Now I know why my rifles haven't a spec of rust.Must surely be because I'm crazy enough to have used WD-40 for years. I do use pressurized air to remove any excess and am careful to keep it off optics (keep it away from caps/primers too).