[dgludwig]

After decades of using WD-40 as a protectant and a lubricant, I learned the hard way of another reason not to use the stuff, especially in areas of small, moving parts. Over time, WD-40, if left in the same confined area, will (or at least can) congeal into a semi-solid, hard, waxy substance that is difficult to remove. If this hardened residue finds itself in a place where tolerances are tight for small working parts to move, it can result in a malfunctioning firearm.