I have a VERY RARE, COLT DELTA EITE This is the Colt Delta H- Bar model R6600DH Cased rifle ( Pre-Ban ) These Very Rare variation of the AR-15A2 converted at the Colt Factory after being selected for accuracy into the DELTA-HBAR. The conversion consisted of the Factory installed Tasco 3-9 power rubberized/armored variable scope with special mount, Colt special cheekpiece for shooting with the scope. It also has all other A2 upgrades such as forward assist,brass deflector adjustable rear sights and heavy barrel H-Bar.  This is a Highly desirable Collector Pre-Ban rifle.

the former owner says its unfired, mags and paper work still sealed in plastic as well.

This is a Pre-Ban Rifle

Rifle Says .223 Rem so I can only assume no 5.56