If its coming out of California, I am assuming that it was an actual LE duty weapon. If this is the case, it was likely subjected to hard use/abuse and this could explain the gas residue. Armalite uses hex screws instead of pins to attach thier FSB, which is bad for a combat weapon. Every Armalite I have ever owned came loose at some point, until they were lock-tited in place which defeats the purpose of having an adjustible FSB. The price is a little high for a hard used LE duty weapon when you can buy a LEO rollmarked AR in brand new condition for that price. In my experience, LEO Armalites are less common than other LEO manufactures which may make them more valuable in the future, but this isn't something one should fret over. I personally haven't had great luck with Armalite, but I sitll reguard them as an excellent manufacture. Nobody gets it right 100% of the time. I have an ISP issue Armalite which I really like and is as good as any of my other AR's and I paid 775.00 for it brand new. I think you can do better.....