Heckler & Koch HK MR556A1 5.56 NATO AR-15, 16.5 in CHF Heavy Barrel, Short-Stroke Piston, Free-Float M-LOK, Factory New
This HK MR556A1 is the U.S. commercial semi-automatic counterpart to the HK416 family, built on a short-stroke gas piston system with a 16.5 inch cold-hammer-forged heavy barrel. It features a free-float M-LOK handguard with a continuous, numbered top Picatinny rail, a collapsible stock, and an ambidextrous safety. Factory new and unfired beyond testing, it comes with the original HK box, manual, tool, lock, and a 30-round Magpul PMAG Gen M3 magazine.
Condition
Overall Condition: Factory new condition, unfired with no signs of handling. Includes all accessories and paperwork in the original factory box/case.
Bore Overall Condition: New - As-new bore with no signs of use beyond factory testing.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: There are very light, superficial scratches from storage and light handling.
What’s Included
- HK tool
- Gun lock
- Manual
- HK factory cardboard box
- 1x 30-round Magpul PMAG Gen M3 5.56x45 polymer magazine
The MR556A1 uses HK's proven short-stroke gas piston action for clean-running, consistent cycling. The heavy-profile, cold-hammer-forged steel barrel is unlined with a swaged (muzzle choke) treatment and a 1:7 twist to stabilize a wide range of 5.56 NATO projectiles. An A2-style flash hider is installed on the threaded muzzle.
Its slim, free-float aluminum handguard provides M-LOK slots and a continuous, numbered top Picatinny rail for mounting sights and accessories. The upper includes a forward assist and case deflector, while the ejection-port cover is a reinforced polymer design with circular strengthening features.
The lower receiver features captive HK-pattern takedown pins with center plungers and an ambidextrous safety that can be engaged with the hammer down. A Magpul pistol grip is installed, and the collapsible polymer stock provides adaptable length of pull. The rifle accepts STANAG-pattern magazines and includes a 30-round PMAG Gen M3.
Hard-coat anodized aluminum receivers, precise machining, and HK's attention to detail round out the build. Markings include Heckler & Koch Inc., Columbus, GA and a shielded 'CC' stamp.