I won't use WD40 on my guns because of the paraffin content. As a machinist I used it as the final step of prepping a machine for a new job after it was stripped and cleaned. Water displacers are good at displacing water. My guns get a combination of stuff depending on what it is and what kind of action but it's generally some light machine oil on the interior and some light mineral oil with an alkyl rust inhibitor on the exterior. Grease in the places that need grease ,of course. Not that I object to WD40 as a lubricant and protective. I don't. It does work and I do use it, just not on my guns because I don't like the feel of paraffin. Did you know: WD40 was never patented and the exact formulations are kept as industrial secrets?