Luxus Arms HM15F-MB-556-L: HM Defense\'s Defender M5 rifle features a HM MonoBloc barrel with an integral machined gas block. The 4150 chromoly barrel also features a mid-length gas system and is match grade, tripled honed, and button rifled. The Defender M5 also utilizes a 15\" free-float handguard with Picatinny rail and is compatible with Magpul M-Lok mounting system. To finish off this tactical firearm is a Mil-Spec HM stock and Magpul MOE grip.