Factory new from Daniel Defense, with DD flash hider pinned and welded for 16" equivalent legal barrel. The Daniel Defense M4A1 Upper Receiver Group features the M4A1 Rail Interface System (RIS II), which has been in use by US Special Operations Command (SOCOM) for the SOPMOD II Weapons System since 2005.
This two-piece, free-floating rail system allows the mounting of devices like a M203 grenade launcher without influencing the barrel's harmonics, eliminating problems like wandering point of impact that plagued other mounting designs. The two-piece design also allows for partial disassembly of the rail to aid in cleaning around the barrel without completely removing the entire rail system. The weight of anything attached to the RIS-II rail system is fully supported by a sturdy bolt-up system, using 6 grade 8 bolts, leaving the barrel completely free floating for best possible accuracy and dependability.
The DD M4A1 Factory Upper Receiver Group features a signature Daniel Defense 14.5” Cold Hammer Forged M4 Profile barrel with a permanently attached extended A2 Flash Suppressor to meet the NFA required 16” length. Daniel Defense complete upper receiver groups come complete with bolt carrier group and charging handle. The DD Mk12 gas block is installed, and that fits the carbine gas system, with the bottom of the gas block extended through a little nook in the bottom of the RIS-II rail.
Note: Upper receivers arrive to us both as new upper receivers from DD, and also as rifles, and we take apart the upper and the lower. Either way, these are factory new. More than likely, the barrel and bolt will show signs of test firing (brass markings).
Manufacturer's Part Number: 23-004-13150
some pictures courtesy of Tactical Life, see article
Daniel Defense
Colt
Daniel Defense
Colt
Daniel Defense
Daniel Defense