HK MR556A1 5.56 NATO Semi-Automatic Rifle – Short-Stroke Piston, Free-Float M-LOK Handguard & Cold-Hammer-Forged 16.5" Barrel
The HK MR556A1 brings the combat-proven HK416 design to the commercial market with a 16.5" cold-hammer-forged barrel, a clean-running short-stroke gas-piston system, and fully ambidextrous controls. Built on 7075-T6 aluminum receivers and fitted with HK’s rifle-length free-float M-LOK handguard, this rifle offers exceptional durability, accuracy, and modularity in a package that stays remarkably soft-shooting and clean.
Condition
Overall Condition: Excellent condition, showing only faint signs of any prior use or handling.
Bore Condition: Excellent – Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent – Sharp lands and grooves.
What’s Included
- HK MR556A1 5.56 NATO rifle
- One 30-round Magpul PMAG GEN M3 polymer magazine
Built around the same short-stroke piston system adopted in the HK416 and the USMC’s M27 IAR, the MR556A1 keeps carbon fouling out of the receiver for enhanced reliability during high-volume fire. The piston assembly also reduces felt recoil and maintains consistent bolt carrier speed, contributing to outstanding parts longevity.
The 16.5" barrel is cold-hammer-forged from premium steel, given a phosphate finish, and features a 1:7" twist to stabilize the full spectrum of modern 5.56 projectiles. HK’s subtle taper toward the muzzle boosts velocity and accuracy while retaining NATO-standard ½"-28 muzzle threads for easy attachment of flash hiders or suppressor mounts.
A rifle-length free-float M-LOK handguard keeps weight forward balanced and provides plenty of real estate for modern accessories without adding bulk. A continuous top Picatinny rail runs from receiver to handguard for simple optics mounting.
The fully ambidextrous lower offers mirrored controls—magazine release, bolt catch, and safety selector—ensuring intuitive manipulation for both left- and right-handed shooters. The six-position HK E1 stock features a rubberized recoil pad, QD sling cup, and a serrated toe designed for barricade support.
Precision-machined 7075-T6 receivers wear a durable hard-coat anodized finish, and the rifle remains compatible with mil-spec AR-15 components thanks to HK’s A1 pin geometry. With an MSRP of $3,499, the MR556A1 delivers service-rifle pedigree and modern ergonomics in a civilian-legal package.