Heckler & Koch MR556 A4 5.56mm (81000827) is a premium, piston-driven AR-platform rifle built for shooters who want HK416-style reliability, top-tier accuracy, and a duty-grade 5.56 NATO carbine. This MR556 A4 configuration pairs a 16.5 inch barrel with ambidextrous controls and an adjustable stock for hard-use defensive, duty, and serious range applications.
Key Features
- Manufacturer part number 81000827
- Model: MR556 A4
- Caliber: 5.56x45mm NATO / .223 Remington
- Barrel length: 16.5 inches, cold hammer-forged
- Operating system: Short-stroke gas piston
- Gas system: Adjustable gas regulator, suppressor-ready
- Barrel thread: 1/2x28, suppressor-ready concentric threads
- Barrel profile and twist: Match profile, 1 in 7 inch right-hand twist
- Handguard: Free float slimline rail with M-LOK slots and continuous top Picatinny
- Receiver set: HK416-style upper with updated magazine well
- Stock: HK416 six-position adjustable stock
- Grip: HK USA enhanced pistol grip
- Finish: Matte black, hard-use external treatment
- Capacity: 30+1 (ships with one 30-round magazine in most configurations)
- Overall length: Approximately 33.25 to 36.5 inches, adjustable
- Weight: Approximately 7.7 pounds without magazine
- Controls: Fully ambidextrous safety, bolt release, and magazine release
- Sights: Optics-ready, no factory iron sights included
Special Features
- Short-stroke gas piston system keeps hot fouling out of the action to support longer firing cycles with less cleaning and reduced parts wear.
- Adjustable gas block allows tuning for suppressed or unsuppressed use, helping maintain reliability across different setups.
- Free-floated rail and match-grade barrel support excellent mechanical accuracy for precision and duty roles.
- Fully ambidextrous controls and extended charging handle make manipulation intuitive for both right- and left-handed shooters.
- HK416 slimline furniture, including the stock and handguard, gives a slimmer, more maneuverable feel compared to older patterns.
Practical Benefits
- The Heckler & Koch MR556 A4 5.56mm (81000827) is well suited for law enforcement duty, defensive carbine roles, and high-volume training where reliability is critical.
- Match barrel, free-float rail, and piston system make it a strong fit for SPR-style builds, competition, and precision-oriented carbine work.
- Adjustable stock and ergonomic grip help a wide range of shooters get a solid, repeatable shoulder and trigger position.
- Optics-ready upper and modern rail system make mounting LPVOs, red dots, magnifiers, and accessories straightforward for custom setups.
The Heckler & Koch MR556 A4 5.56mm (81000827) is a proven platform and capable tool for shooters seeking a top-tier, piston-driven 5.56 rifle for duty, defense, and serious range use.
| MANUFACTURER | HECKLER & KOCH |
| MODEL | MR556 A4 |
| CALIBER | 5.56MM |
| TYPE | RIFLE |