No, WD40 is not a proper lubricant; that much is certain. However relative to other common uses, I find it works as well as Kroil. Just a personal opinion.
As far as guns, if I didn't have anything else, I would use it as a cleaning solvent, followed by drying it off and then a good lubricant.
Someone mentioned Marvel Mystery air tool oil. While I've never used it, I've heard/read good things about it, and just today saw it in Walmart for 15 bucks a gallon. That's cheaper than ATF, though personally I'm sticking with my well proven ATF.
Vettepilot
