The M4-89 is one of the premier fighting rifles we offer. It houses a combat grade barrel, A5 buffer system, Liberty Fighting Trigger, and B5 furniture. At Sons of Liberty Gun Works, they always tell their customers that it's not what a rifle company tells you, it's what they don't tell you. Below you will find the complete specifications of the M4-76. SOLGW builds their guns to run through years of hard use, and they have nothing to hide. Barrel: Sons of Liberty Gun Works 4150CoMOV 1:7 MPI HPT Barrel Barrel Steel: 4150 CrMoV (Chrome Moly Vanadium per MIL-B-11595E) Twist Rate: 1/7 Twist Six Groove Thread Pitch: 1/2-28 Threaded Muzzle Gas Blo Mfg: Sons Of Liberty Gun Works