An M16 is always an automatic weapon. Any automatic weapon is a machine gun.
Regardless of this whole 'assault rifle' happy horseshit (which is a misnomer really, but, seriously bro, just watch the History Channel or some shit, WW2 Guns or I Don't Know a Fucking Thing About Guns or a program I gueststarred on, Dirty Jobs : Talking To Idiots Online), there's no way there are any M16s for sale at Cabela's, let alone for $800.
Maybe $18,000, but still not Cabela's.
Please, just let this go, you are wrong tonight. Wrong tomorrow. Wrong on Thursday.
Back on topic, Raith's setup is the cheapest, reliable AR15 you're going to find.
Good, fast, cheap, pick two.