Heckler & Koch MR556A1 5.56 NATO Semi-Automatic Rifle — 16.5" CHF Barrel, HK416-Style Short-Stroke Piston, M-LOK Handguard
The MR556A1 brings the battle-proven HK416 operating system to a civilian-legal platform, delivering excellent reliability and accuracy in a package built with Heckler & Koch’s meticulous manufacturing standards. This example features a cold-hammer-forged chrome-moly barrel, ambidextrous controls, and a free-float rifle-length M-LOK handguard, making it a standout for shooters who want military lineage with modern modularity.
Condition
Overall Condition: Excellent condition, showing only faint signs of any prior use or handling.
Bore Condition: Excellent – clean, mirror finish with sharp lands and grooves.
Specific Condition Notes: Minor, superficial scratches and blemishes are present on the exterior but have no effect on function.
What’s Included
- Heckler & Koch MR556A1 rifle
- HK-branded padded soft rifle case
- 1× 30-round steel STANAG magazine
- 3× 32-round polymer magazines
- HK flip-up front and rear iron sights (installed)
This MR556A1 uses a closed, short-stroke gas piston that keeps fouling out of the receiver for cleaner, more reliable operation than direct-impingement systems. The piston design mirrors the HK416, a platform trusted by professional users worldwide.
The 16.5-inch cold-hammer-forged barrel is made from chrome-moly steel, left unlined to preserve HK’s proprietary taper-bore geometry. The 1:7-inch twist stabilizes both standard and heavier match bullets, while the 1/2-28 threads accept a wide range of muzzle devices.
A free-float aluminum M-LOK handguard provides ample real estate for accessories without contacting the barrel, supporting the rifle’s accuracy potential. Flip-up iron sights come installed, and the flat-top receiver is ready for optics.
Ambidextrous controls include the safety selector and magazine release, making the rifle user-friendly for right- or left-handed shooters. The six-position collapsible stock adjusts quickly for length of pull, and drainage ports in the barrel allow safe firing after submersion.
Built on hard-coat anodized 7075-T6 receivers, this rifle accepts standard MIL-SPEC AR-15 parts and magazines, offering parts commonality while maintaining HK’s renowned build quality.