HK MR556A1 5.56mm NATO 16.5in Black Semi-Automatic Modern Sporting Rifle – 10+1 Rounds

The HK MR556A1 5.56mm NATO rifle is a civilian-grade descendant of the legendary HK416, engineered for shooters who demand premium reliability, tactical performance, and match-grade accuracy. This semi-automatic rifle is ideal for home defense, precision target practice, competitive shooting, and AR-style tactical training. The MR556A1 uses Heckler & Koch’s proprietary gas piston system, providing unmatched durability and cleaner operation compared to traditional direct impingement AR-style rifles.

Cold Hammer-Forged Barrel & Precision Engineering

Featuring a 16.5-inch barrel manufactured using

HK MR556A1 5.56mm

cold hammer forging process, the MR556A1 ensures superior longevity and tight groupings. Its thick, heavy-contour design and 1:7 twist rate optimize performance with

HK MR556A1 5.56mm

ammunition, making this rifle ideal for long-range shooting, competitive 3-gun events, and tactical drills.

HK Proprietary Gas Piston Operating System

The MR556A1’s short-stroke gas piston system uses a solid operating “pusher” rod in place of the standard AR gas tube. This keeps hot gases and carbon fouling out of the receiver, reducing wear and maintenance while increasing reliability under adverse conditions. Shooters experience smoother cycling, extended shooting sessions, and enhanced component longevity.

Modular Free-Floating Rail System & Optics Ready

The MR556A1 features a Free-Floating Rail System (FFRS) handguard with four MIL-STD-1913 Picatinny rails for maximum accessory customization. The top rail on the upper receiver allows optics, scopes, or tactical sights to be mounted easily. The rail system is designed to return to zero when reinstalled, ensuring consistency for precision shooting. Major subassemblies, including the upper receiver/barrel assembly, are fully interchangeable with other high-quality AR-style firearms, allowing upgrades or retrofits of legacy AR platforms.

Features and Accessories

• 10+1 round magazine for range and practical shooting
• Adjustable diopter front and rear sights
• Full-length MIL-STD 1913 optical rail for scopes or red dot sights
• Black polymer fixed buttstock for lightweight durability
• HK Free-Floating Rail System handguard for maximum accessory versatility
• Cold hammer-forged 16.5-inch barrel with 1:7 twist optimized for 5.56mm NATO ammunition
• Proprietary short-stroke gas piston system for clean, reliable operation
• Upper receiver/barrel assembly fully interchangeable with other high-quality AR-style rifles

Specifications

Action	Semi-Automatic
Capacity	10+1
Barrel Length	16.5 in
Cartridge	5.56mm NATO
Color	Black
Finish	Black
Gun Model	MR556A1
Hand	Right
Weight	8.6 lbs
Overall Length	33.9 in – 37.7 in
Twist	1:7 in
Sights	Adjustable Diopter Front & Rear / Full-Length MIL-STD 1913 Optical Rail
Stock	Black Polymer Fixed Buttstock
Grips	Black Polymer
Product Line	MR556A1
State Compliance	Colorado Compliant
Type	Centerfire

Why Choose the HK MR556A1 10+1 Semi-Automatic Rifle?

The HK MR556A1 delivers military-grade reliability and AR-style versatility for civilian shooters. Its proprietary gas piston system, cold hammer-forged barrel, and free-floating rail system make it perfect for home defense, tactical training, competitive shooting, and precision target practice. Fully compatible with other AR-style assemblies and optics-ready, the MR556A1 provides accuracy, durability, and tactical adaptability for the modern shooter.