What's in the Box Colt M4 5.56 NATO Mid Length Carbine (1) 30 Round Magazine Owner's Manual The Colt Carbine offers incredible precision and performance with a reliable, lightweight, and a durable rifle design. This AR-15 rifle is chambered in 5.56 NATO and has a 16." barrel. Firearm Features Adjustable Stock M-Lok Forearm M4 Chrome Lined Barrel Firearm Specifications Manufacturer: Colt Model: M4 Mid Carbine Caliber: 5.56x45mm NATO Barrel Length: 16" Twist: 1:7" Overall Length: Finish: Black Synthetic Grips: Polymer Sights: None, Optic Ready Magazine Capacity: 30+1