The Heckler & Koch MR556 A4 is a semi-automatic rifle built around the commercial version of the HK416 operating system. Its short-stroke gas piston system keeps hot carbon fouling out of the action, supporting cleaner operation and reduced maintenance. A two-position adjustable gas regulator allows the rifle to be configured for suppressed or unsuppressed use. The match-grade cold-hammer-forged barrel is suppressor-ready with 1/2x28 muzzle threads, while the continuous Picatinny rail and M-LOK handguard provide a flexible platform for optics, lights, and other accessories. Fully ambidextrous controls, including the 45-degree safety selector, bolt release, and magazine release, improve handling for right- and left-handed shooters.

Key features

• Short-stroke gas piston system helps keep the action cleaner than direct-impingement designs
• Two-position adjustable gas regulator supports suppressed and unsuppressed operation
• 16.5-inch match-grade cold-hammer-forged barrel with suppressor-ready 1/2x28 threads
• Continuous Picatinny rail and M-LOK handguard support optics and accessories
• Fully ambidextrous safety, bolt release, magazine release, and QD controls
• 30+1 capacity provides substantial ammunition capacity for training and field use

The MR556 A4 combines HK416-derived piston reliability, ambidextrous controls, and a versatile accessory-ready design in a durable 5.56 NATO rifle.