Heckler & Koch MR556A4 Upper Receiver Kit AR-15 Compatible 5.56 NATO 11" Barrel Matte Black Finish

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.

• Piston-driven operating system for enhanced reliability
• Stainless steel 11.5" barrel with 1-in-7" twist
• Free-floating M-LOK handguard for accessory mounting
• Extended charging handle and ambidextrous QD sling cups

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.