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The HK MR556A4 Upper Receiver Kit is a premium 5.56mm/.223 Rem upper assembly designed to upgrade your AR-style pistol with Heckler & Koch's renowned piston-driven operating system. This closed-bolt system virtually eliminates the malfunctions associated with direct-impingement gas systems, ensuring reliable performance even in the harshest conditions. Featuring an 11" stainless steel barrel with a 1-in-7" twist rate, the MR556A4 delivers exceptional accuracy and velocity. The free-floating M-LOK handguard provides a sturdy, lightweight platform for mounting accessories, while the extended charging handle and ambidextrous QD sling cups enhance ergonomics and versatility.
Whether you're building a new AR-style pistol or upgrading an existing one, the HK MR556A4 Upper Receiver Kit is an exceptional choice for discerning shooters who demand the best in performance and reliability.
