COLT 6721 UPPER FOR SALE FOR DUMMIES

Note:  The Colt 6940 loved ones of rifles are proprietary built, with couple person serviceable parts.  Specific tools are needed to eliminate the barrel nut and barrel.  The gas program is exclusive rather than made to get replaced with mil-spec parts. Great news, MK18 upper arrived currently from Principal Arms.  Looks great.  I need to fin