Naaa......don't tattle tail. Just move on and don't bother with him. It does sound like bull**** though. Their are NO post 1986 class C's. Legal that is. If he's destined to get it from the ATF then that's his problem. He might get some unsuspecting stupe in trouble too, but that is still not you businesses. If your not a cop than don't do their job.
Still why an SKS, their junk. It only has ten rounds and is slow to reload. Now a lightning link in an AR15 or modding a Cobray pistol is something I can understand. Huh....some people.
Hey, I think I got it. If the full auto thing is not bull**** than I bet it's a malfunction. His safety sear must have broke. The guy started bragging that he did it on purpose instead of getting it fixed, though I dough he could ever duplicate the result in another gun. If this is the case than the resulting full auto is strictly a malfunction and thus is dangerous. The thing about it being legal is total bull**** and he's to damn dumb to know how much trouble he could get in if ATF does come after him, witch they may or may not depending on the branch that works that aria. That's evident by the fact that he's announcing it to the whole net. Either way just avoid the guy and let the real Law Enforcement Professionals deal with it. It's their job not yours.