That link is from a locksmith who states emphatically that WD-40 does not gum up, whereas he says 3 in 1 oil does. He says he's used WD-40 on locks for over 30 years with no problems. And if it won't gum up lock tumblers, it's a real safe bet that it won't gum up gun lock-work, as is commonly alleged.
You know when you mentioned this about locks i was told by a locksmith to use it liberally in an older model gm that wouldn't move. Surely enough i doused it inside and the key turned and never failed again. He said that we often deposit the buildup from our dirty keys in the tumbler every time we start the car and the WD-40 breaks the gunk down and walla!