Hi,
Recently had a conversation with a person from the Dutch army about WD40-useage. His explanation was that WD40 worked too good and could cause quicker wear of the bore, as the normal gun oils and dirt tend to fill up microscopic defects in the bore, thus reducing wear and tension on these defects. WD40 cleans out these defects, with the result that the discharge of a round hits the defects harder and longer, leading to faster wear.
If there is any truth to this story, using WD40 on the gun outside wouldn't be a problem, just don't use it to clean out the bore when you intend to shoot the hell out of it. Something that isn't pretty important for collector grade guns.
Fish oil. Hmm. Makes sense, those critters displace water pretty well
