Made with pride in the USA, CMMG's Mk4 HT, 5.56MM SBN Upper Group builds the foundation of a workhorse semi-automatic rifle. CMMG's RKM11 KeyMod™ free-float handguard adds attachment points for all types of tactical accessories for true modular customization. The heavy-taper SBN, 16.1" barrel is crafted from 4140CM steel, has 1:7 rate-of-twist rifling and comes equipped with a muzzle with thread protector (1/2-28"). Upper group components include forged 7075-T6 AL M4-type receiver; barrel sub assembly; charging handle; bolt-carrier group; handguard and barrel nut. Made in USA.