Heckler & Koch MR556 A4 5.56mm SBR 11" Barrel - 30 Rd

Heckler & Koch MR556 A4 5.56mm SBR 11" Barrel - 30 Rd

The Heckler & Koch MR556 A4 Short Barrel Rifle 11" represents the pinnacle of modern 5.56×45 NATO rifle engineering, combining legendary Heckler & Koch reliability with a compact 11-inch short-barrel configuration built for maximum maneuverability without sacrificing control or precision. Designed on HK’s battle-proven piston-driven architecture, this A4 variant delivers elite-level durability, reduced fouling, and consistent performance in the harshest conditions.

The MR556 A4 features a short-stroke gas piston system that prevents carbon and heat from entering the receiver, significantly reducing wear and extending operational life. Its adjustable gas regulator allows seamless tuning for suppressed or unsuppressed shooting, making it adaptable across a wide range of mission profiles. Paired with a cold hammer-forged barrel and refined internal components, this platform is built to run harder, longer, and cleaner than traditional direct impingement systems.

With its continuous top rail, free-float M-LOK handguard, and fully ambidextrous controls, the MR556 A4 is optimized for modern accessory integration and intuitive handling. Whether configured for duty, defensive use, or professional training environments, this rifle delivers the confidence of HK’s engineering legacy in a compact, high-performance package.

HK Short-Stroke Gas Piston System
Keeps hot carbon fouling out of the receiver for cleaner operation, reduced maintenance, and extended component life.

11” Compact Barrel Platform
Delivers enhanced maneuverability in tight environments while maintaining strong 5.56 NATO ballistic performance.

Adjustable Gas Regulator
Enables tuning for suppressed or unsuppressed operation to optimize reliability and recoil characteristics.

Cold Hammer-Forged Barrel
Built for exceptional durability, heat resistance, and long-term accuracy under sustained fire.

Free-Float M-LOK Handguard
Improves accuracy potential while allowing secure mounting of modern rail accessories.

Ambidextrous Controls
Designed for both right- and left-handed shooters with intuitive, mirrored operation.

Extended Ambidextrous Charging Handle
Enhances manipulation speed and ergonomics under stress or tactical conditions.

QD Sling Integration Points
Built-in quick-detach sling mounts for adaptable carry and transition options.

Specifications

• Caliber: 5.56×45 NATO
• Action Type: Semi-Automatic
• Operating System: Short-Stroke Gas Piston
• Barrel Length: 11 inches
• Barrel Type: Cold Hammer-Forged
• Barrel Twist Rate: 1:7” Right-Hand Twist
• Rifling: 6 Lands & Grooves
• Charging Handle: Extended Ambidextrous Charging Handle
• End Plate: Ambidextrous QD End Plate
• Magazine Capacity: 30 Rounds
• Magazines Included: 1
• Magazine Type: Detachable Box Magazine
• Overall Length: 27.9 in – 31.7 in
• Weight: 7.67 lbs
• Height: 7.5 in
• Width: 3.07 in