The original formulation of WD-40 was notorious for turning into varnish muck like the varnish from leaded gas formed on your car's carburetor. In the late 70's early 80's I was working in the gunsmithing shop at Browning Arms in St. Louis, can't tell you how many BT-99 trap guns I worked on whose actions had been rendered inoperable from accumulations of varnish from WD-40 use. I'm told that sometime after that period the formulation of WD-40 was changed so that varnish formation is no longer an issue.
Since WD-40 stands for Water Displacement formula 40, if the formulation was changed, shouldn't it now be called WD-41? I too saw too many problems with its use on firearms to avoid it. There are so many other better products out there, so I see no use in having it anywhere near my firearms.
