HK MR556A1 5.56mm NATO Semi-Auto Rifle – 16.5" CHF Barrel, Short-Stroke Piston, M-LOK Handguard
The HK MR556A1 is the civilian version of the combat-proven HK416, built in Columbus, Georgia from German-forged 7075-T6 receivers. Its closed short-stroke piston system runs cleaner than direct-impingement designs, while a cold hammer forged, nitrided 16.5-inch barrel delivers long service life and consistent accuracy. A lightweight free-float M-LOK handguard, six-position HK E1 stock, and two Magpul PMAGs round out this premium AR-platform package.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Condition: Excellent – Clean, mirror finish, no signs of wear.
Rifling Condition: Excellent Rifling – Sharp lands and grooves.
Specific Condition Notes: Minor, superficial scratches and small blemishes are visible on the exterior surfaces; the bore remains clean and shiny.
What’s Included
- HK MR556A1 5.56mm rifle
- Two 30-round Magpul PMAG magazines (Gen M3 Window and Gen M2 MOE)
The MR556A1 uses HK’s proven short-stroke gas piston with a solid operating rod, keeping fouling out of the receiver for enhanced reliability during extended strings of fire.
Its 16.5-inch barrel is cold hammer forged from Cr-Mo-V steel, then nitrided for corrosion resistance. A medium contour balances weight and heat dissipation, while a threaded muzzle accepts standard 1/2×28 devices.
The free-floating aluminum handguard attaches directly to the barrel nut and features M-LOK slots along its length, giving shooters ample real estate for accessories without the heft of older quad-rail systems.
HK’s E1 six-position stock combines a rubber butt-pad, integral QD sling points, and an extended length-of-pull range, paired with a Magpul MOE pistol grip for a secure, ergonomic firing hold.
Forged upper and lower receivers wear a matte black hard-coat anodized finish and carry the HK “CD” forge code plus Columbus, GA import marks, documenting U.S. assembly from German components.