The M153GN are Armalite s flagship competition rifles that are built to win. This carbine is compact light and ultra-fast. The low profile handguard covers a free-floating 13.5-in. barrel with Armalite s own tunable muzzle brake pinned and welded to create a 16-in. barrel. An adjustable gas block also allows the rifle to be individually set for optimal performance. Safety: Ambidextrous Gas system: Adjustable Charging handle: Raptor Ambidextrous Model: M-15 3-Gun Caliber: 5.56X45 mm / .223 Barrel: 13.5 stainless steel Rifling Twist: 1:8 RH Muzzle Device: Armalite tunable brake pinned / welded brake to make the external length 16 Front Sight Base: 2 MIL-STD 1913 rail section at forward 12 o clock position of handguard Upper Receiver: Forged flat-top with MIL-STD 1913 rail 7075-T6 aluminum Lower Receiver: 7075-T6 aluminum (forged) Trigger: Timney 3 lb. single-stage Stock: MBA-1 light weight precision adjustable for length-of-pull and comb height Overall Length: 34.5 / 35.5 Weight: 6.6 lbs. Finish: Anodized aluminum upper/lower receiver Included with Rifle: One 30-round Magpul PMAG limited lifetime warranty