HK MR556 A4 5.56 NATO Rifle, 16.5″ Threaded Barrel (81000827)
The H&K MR556 A4 is Heckler & Koch’s semi-auto rifle derived from the HK416. This 16.5″ model runs on a short-stroke gas piston with a two-position adjustable gas regulator, and has fully ambidextrous controls and a free-floating M-LOK handguard. It ships with one 30-round magazine.
Why choose the MR556 A4
- Piston-driven: hot gas and carbon fouling stay at the front of the rifle instead of blowing back into the action, so it runs longer between cleanings with less internal wear. The trade-off is a higher price than a comparable direct impingement AR.
- Suppressor-ready: the barrel is threaded 1/2×28, and the adjustable regulator has settings for suppressed and unsuppressed shooting.
- Cold-hammer-forged barrel: H&K guarantees the bore against wear for life.
- Ambidextrous: the safety, magazine release, bolt release and charging handle work from either side.
- Refined A4 design: H&K lists lighter weight and a slimmer profile than the earlier MR556A1.
Optics and setup
No sights are included. The full-length top Picatinny rail is ready for an optic, and the M-LOK handguard takes lights and accessories. Shop red dots, scopes, weapon lights, AR magazines, 5.56 NATO ammo and suppressors.
Specifications
- Model: Heckler & Koch MR556 A4, part number 81000827
- Caliber: 5.56x45mm NATO
- Barrel: 16.5″, 1:7″ right-hand twist, concentric 1/2×28 threads
- Action: semi-auto, short-stroke gas piston
- Capacity: 30+1, one 30-round magazine included
- Weight: 7.67 lb without magazine
- Overall length: 33.25″ to 36.5″ (stock collapsed to extended)
- Handguard: free-floating M-LOK with top Picatinny rail
- Stock: 6-position, black synthetic
Buy it in Benton, Louisiana
Availability changes quickly, so check the listing or call 318-742-1685. Firearms are transferred through a licensed FFL, and our FFL transfer service explains how. This model cannot be sold to Illinois (PICA) and cannot ship directly to California, Rhode Island or Washington. More from Heckler & Koch.
FAQ
Is the MR556 A4 an HK416?
No. H&K describes it as the commercial variant of the HK416. It shares the piston design but is semi-automatic only.
Does it come with sights?
No. You’ll need to add an optic or backup sights.
Will it take standard AR magazines?
H&K says the angled magazine well is designed for reliable feeding from AR-pattern magazines, and one 30-round magazine is included.
Can I run a suppressor on it?
Yes. The barrel has concentric 1/2×28 threads. Confirm your suppressor’s mount, and check the H&K manual for the correct gas regulator setting.
Can I buy it outside Louisiana?
In most states, yes, through an FFL transfer, subject to the state restrictions above.
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