Manufactured between 1973 and 1982, this vintage pre-1986 Colt M16 lower receiver has been upgraded with a later production A4 patter upper receiver assembly outfitted with an A.R.M.S. SIR free-floating handguard, giving the flexibility of current "modern sporting rifle" design in a fully transferable automatic weapon. Post front and pop-up adjustable two leaf rear sights, closed-bottom birdcage flash hider on the 1/9" twist barrel, and a bayonet lug. The lower has the traditional Colt model markings and address on the left side, with a "SAFE/SEMI/AUTO" marked right-handed selector switch, checkered pistol grip, and a Bushmaster brand 6-position telescoping buttstock. The bolt carrier and bolt head are both matte gray finished, and a one piece buffer is installed. A canvas soft case is included.