I also think there are better products out there than WD40. I use G-96 gun treatment on all of my firearms. I spray it on, let it sit for a little while (60 sec) then wipe it off, re-apply as needed. I haven't had a problem with is yet. Another thing great about G-96 is that it's also a very good cleaner and I use it to clean every part of my firearms except the bores. This way, with athorough cleaning I'm also protecting all the little parts and pieces I've cleaned. After I'm done cleaning the barrels, I spray a shot of G96 down the bores and I'm good to go.

I trust it even on my oldest of guns.