HK MR556 A4 5.56 NATO Semi-Auto Rifle, 16.5 in Cold Hammer Forged Barrel, Short-Stroke Piston, Earth-Tone Finish
The MR556 A4 is Heckler & Koch's commercial counterpart to the HK416, combining a 16.5 in cold hammer forged barrel with a proven short-stroke gas piston system. This example adds a two-position gas regulator marked N/S for suppressed/unsuppressed use, fully ambidextrous controls, and a continuous T-marked Picatinny top rail. The earth-tone receiver finish, free-float aluminum M-LOK handguard, and included accessories make this a feature-complete, modern 5.56mm NATO rifle.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Overall Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: Minor, superficial scratches and blemishes are present on exterior surfaces from prior handling. One of the M-LOK sections has minor damage from a previously mounted attachment.
What’s Included
- Original case
- Straps for carry case
- Toolset
- 2x 30rd Magpul PMAG Gen M3 polymer AR/M4 magazines
- M-LOK QD sling cup (installed on handguard)
The MR556 A4 operates on HK's short-stroke gas piston system and features a two-position gas regulator marked N/S for suppressed or unsuppressed settings. This setup delivers consistent cycling with a wide range of ammunition while keeping fouling out of the receiver.
Its 16.5 in cold hammer forged, non-fluted barrel uses a 1:7 RH twist for modern 5.56mm projectiles and is threaded at the muzzle with a birdcage flash hider. The bore condition and rifling are excellent, reflecting minimal use.
Controls are fully ambidextrous, including the selector, bolt catch/release, and a dual-latch ambidextrous charging handle. A 6-position collapsible stock and HK ergonomic pistol grip provide adaptable fit and secure handling.
The free-float aluminum M-LOK handguard includes an integrated QD sling cup, and this rifle also has a separate M-LOK QD sling cup installed. A continuous, T-marked Picatinny top rail measures approximately 20.3 in for mounting as needed. The receiver wears an earth-tone finish, with proof marks/import stamp from Heckler & Koch Inc., Columbus, GA. Capacity is 30+1, and two Magpul PMAG Gen M3 magazines are included.