Daniel Defense M4A1 Mil Spec and Semi-automatic AR, 223 Rem/556NATO, 14.5 Hammer Forged Barrel (16 OAL with Pinned Brake), Carbine Length Gas System, Matte Finish, Brown, Daniel Defense Furniture, 32 Rounds, 1 Magazine 02-088-15126-011 The Daniel Defense M4A1 features the M4A1 RIS II, which has been in use by US Special Operations Command (SOCOM) for the SOPMOD II Weapons System since 2005. The M4A1 features a 14.5" Cold Hammer Forged M4 Profile barrel with a permanently attached Daniel Defense Flash Suppressor.