My opinion on WD40 - is stay away from it in a hi heat situation! Here's my ancedotal evidence against the stuff: about two decades back (1987) I was doing some work as an armorer and I was putting a beautiful old German MG34 (the world'd first, and in my opinion, still the best, general purpose belt-fed machine gun) through its paces. I had cleaned and lubed the gun and link belts, as prescribed in the German armorer's manuals, but I had used WD40 as the lubricant as opposed to good old fashioned standard gun oil or light machine oil. I let rip five linked belts (50 rounds per belt at 950 rpm goes very fast) - with no problem; then I went for extended defensive fire (sawed down a foot thick pine tee at one hundred yards) - for five hundred rounds and changed barrels (the receiver, bolt and barrel shroud were heating up nicely); then I went for another extended 500 round romp and I noticed that the gun's timing was starting to slow - I was down to about 650 - 600 rpm and I stopped shooting. I lifted the feed tray cover to find something akin to bubble gum - in long sticky strands all over the working mech. The WD40 had reached its limit and had turned to a new substance - a lot like bubble gum and just as sticky! Cleaning was not a lot of fun but I learned a valuable lesson - heat and WD40 do not mix well! So, I never use it on anything critical in my Landi or anything else for that matter