H&K MR556 A4 | 5.56 NATO | 11″ Barrel | 30+1 | 81001201

The MR556 A4 uses a short-stroke gas piston system that reduces hot carbon fouling in the action for longer sustained operation and lower maintenance. An adjustable gas regulator supports both suppressed and unsuppressed operation, and fully ambidextrous controls simplify handling for right- and left-handed users. The rifle’s M-LOK handguard and threaded 11″ barrel make it a compact, serviceable platform for range use and professional duty applications. A good optic pairing under $1,000 is the Vortex Strike Eagle 1-6×24, which offers a versatile magnification range and rugged construction suited to this platform.

Product Specifications

• The manufacturer part number is 81001201.
• The UPC is 642230271050.
• The cartridge is .223 REM/5.56 NATO.
• The barrel measures 11 inches and is threaded.
• The action type is Semi-Auto.
• The listed capacity is 30 + 1.
• The overall length is 26.50 inches.
• The weight is approximately 6.61 lbs.
• The weight range is given as 6 lbs to 6.99 lbs.
• The stock material is Synthetic with a Black finish.
• The grip material is Black Polymer.
• The handguard style is M-LOK.
• The firearm features a short-stroke gas piston operating system and an adjustable gas regulator for suppressed or unsuppressed use.
• The controls are fully ambidextrous, including an ambidextrous safety lever.

The MR556 A4 is purpose-built for users who need a low-maintenance, compact 5.56 platform with contemporary accessory compatibility. Its piston-driven operation and adjustable gas system reduce routine cleaning and allow tailored function with suppressors or specialty ammunition, while the M-LOK handguard and threaded barrel make mounting optics and accessories straightforward. Whether you prioritize dependable performance for sustained range training or a compact, serviceable rifle for professional applications, this A4 configuration offers a balanced set of features without unnecessary complexity.

Owners commonly report that the piston system reduces fouling in the action and that the rifle has solid build quality and reliable function.