Quoted: With this display get within the SAS vid, the pivot pin manager sure looks reprofiled to me. Both radii are actually cut The "C" on the barrel would suggest a chrome chamber only barrel. But AFAIK, Colt marked the "C" up close to the muzzle on their own early https://coltcombatunitrailgun4555555.national-wiki.com/1069009/indicators_on_colt_m16a1_for_sale_you_should_know