The HM Defense Defender M5 is a direct gas impingement AR-15 style semi auto rifle chambered in the popular 5.56 NATO cartridge. The most interesting point on this rifle is the use of the HM Monobloc barrel which features a gas block that is integrally machined as part of the barrel. This eliminates the need to align the gas block. Also you will notice improved barrel harmonics which translates into better accuracy and dependable performance in severe conditions. - CALIBER 223 REM/5.56MM NATO - MAGAZINE (1) 30rd capacity - BARREL 16" 4150 Chromoly, 1:8 twist, CNC Machined Muzzle Brake threaded 1/2x28 - RECEIVERS M5 Forged 7075-T6 Aluminum - HANDGUARD 12" Free Float M-LOK 6061-T6 Aluminum - TRIGGER Mil-Spec - STOCK Mil-Spec HM