WD-40 and CRC2 were developed primarily for water displacement, or to protect items from moisture. It is effective as a lubricant, and has a thousand other uses, everything from a fish attractor to a treatment for arthritis. While working with Air Force Water Transportation out of Port O'Connor Texas we bought both by the 55 gallon drums, you could spray a water soaked ignition system or distributor and almost always get the motors to start. I have used WD-40 on guns for years and never had a problem myself, however, after getting into a situation where she thought she needed her gun my wife removed her Mauser HSc from her purse and drove home with it in her lap. When she arrived, she related her story to me and said I haven't fired my gun in several years, I want to go out tomorrow and shoot it. The following day we went to the range, after setting her a target she picked the gun up, sighted it and pulled the trigger. CLICK! I cleared the gun and tried it myself, Click, Click. I took the gun home and tore it down, it was jammed full of a sticky substance that felt a little grainy. After looking I determined it was tobacco. At that time she smoked, she carried the gun in a Crown Royal bag in her purse. The tobacco and got from her cigarette case into the bag into the gun. I removed the grips, soaked the gun overnight in a solvent, blew it out the following day and put a coat of WD-40 on it and back to the range. The gun hasn't missed a beat since, but she had lost confidence in it and now carries a Model 36 Smith.
I still use WD-40 on occasion, but prefer a mixture of Automatic Transmission fluid and solvent as a rust preventive and gun oil.