I've used nothing but Wolf 223 and X39 for years, never had a problem with it, I've shot the MGM Ironman 4 times and never a glitch, and frankly, it will shoot right down there with my abilities. I do like the poly stuff they make now, but I never had a problem with the laqured stuff like some folks seem to talk about, and I've shot my bushy upper on a friends 16 lower, 90 rounds full auto with no let up except to change mags, still no problems.
I've heard all the story's about it killing extractors by the gross, never happened to my rifle, I even called Bushmaster to ask if they knew of a