ORIGINAL: vadeerkiller
I'll have totake a different path than most of you. Been using WD-40 on the exterior metal of my firearms for 20 years with no problems.Try this test, take 2 pieces of scrap metal and hit them with a wire brush or grinder to get them shiny.Putyour favorite gun oil on one and WD-40 on the other. Then put them outside in the elements for a couple of days. If no rain is in the forecast then hit them with the sprinkler. After a couple of days see which one has more rust on it.
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I have tried it and WD failed miserably. It was a base to a drill press. It was all the time rusting. So I hit one side with WD, and one side with remoil, the cheapest, and thinnest of all oils. The remoil never did rust, the WD did. Shooters Choice is what I like best of all.
Your not going to find too many machinist, watch makers, clock makers, or anyone that needs long term lubercation recommend WD40 for thier trade. I used to see folks all the time in the duck blind hitting thier semi auto shotguns with wD. And they actually wondered why they jammed. I only use dry lube in the action of my gas shotguns. I wipe out all oils. I have yet to have a jam with this procedure.