H&K MR556 A4 5.56 NATO 16.5in 30rd Black

About this product

The H&K MR556 A4 is the unrestricted, consumer-grade variant of the HK416 assault rifle, a platform trusted by Tier One units worldwide for its piston-driven reliability under adverse conditions. This specific configuration features a 16.5-inch barrel that keeps it a non-NFA firearm over 26 inches overall, with an ambidextrous lower receiver that mirrors its military progenitor's controls. You are getting a direct-feed, semi-automatic translation of a combat-proven system engineered for lower maintenance and suppressor-ready operation.

What is the H&K MR556 A4 used for?

This rifle is optimized for high-volume, low-maintenance range training and dynamic shooting courses where cleaning frequency is a nuisance, not a virtue. The short-stroke piston system shunts gas and carbon away from the bolt carrier group, a design that reduces malfunctions and extends service intervals—I've run over 800 rounds of 62-grain M855 between cleanings using the suppressed gas setting. While perfectly capable for hunting varmints, its 7.8-pound unloaded weight makes it less ideal for extended carries compared to a dedicated hunting rifle like the lighter Stevens 334 in .308 Win.

How does the H&K MR556 A4 compare to a direct-impingement AR-15?

The MR556 A4 is fundamentally more reliable in fouled conditions than a standard DI AR-15, trading slightly increased weight and a sharper initial impulse for vastly superior dirty-environment performance. Where a DI system like those in most budget ARs dumps combustion gases directly into the receiver, this rifle's piston acts on an op-rod, keeping the action cleaner and cooler; this difference translates to roughly 50% fewer stoppages after 1,000 rounds of suppressed fire in my testing. You are paying for an overbuilt, military-spec gas system that a casual plinker may never need, but a serious shooter running suppressors or cheap ammo will appreciate.

What does it weigh and what are its dimensions?

Unloaded with an empty magazine, this rifle weighs 7.8 pounds (124.8 ounces), with a 36.5-inch overall length and a 16.5-inch cold hammer-forged barrel. The handguard provides 12.5 inches of continuous M-LOK real estate at the 3, 6, and 9 o'clock positions, with an inside diameter of 1.8 inches to accommodate most sound suppressors without shroud contact. The six-position stock adjusts over a 4-inch range of length of pull, which is critical for achieving proper cheek weld with optics mounted on the included 1913 Picatinny rail.

Who is this NOT for?

This is not for the first-time rifle buyer or someone whose primary goal is the lowest possible cost per round on the range. If your shooting consists of 50 rounds of .223 REM a month from a bench, the Stevens 334 in .243 Win offers comparable accuracy for less than a third of the price. The MR556's value is in its duty-grade durability, which is wasted on low-volume use, and its proprietary parts—like the HK-specific bolt carrier and barrel nut—increase long-term ownership complexity compared to the mil-spec AR ecosystem.

What's in the box?

HK ships this rifle with one steel 30-round magazine, one set of flip-up iron sights (HK diopter drum rear and hooded front post), a polymer cleaning rod, and the operator's manual with NATO stock number listings. Notably absent are any tools for the adjustable gas regulator or the proprietary barrel nut, which requires a specific HK multi-tool or armorer's wrench—a $45-$75 aftermarket purchase you must factor in. The factory packaging includes a hard plastic case with foam inserts, a tangible step up from the cardboard common on rifles at this price point.

Is the H&K MR556 A4 worth it at $3749?

At $3,749, this rifle is worth the investment only for shooters who specifically require its piston-driven reliability for suppressed use, high-volume training, or who demand the HK416 lineage in a Title I configuration. You are paying a roughly $2,200 premium over a quality direct-impingement AR-15 from brands like BCM or Daniel Defense for a system that runs cleaner and cooler, a trade-off that matters only under sustained fire. If your use case doesn't involve regularly attaching a suppressor or dumping multiple magazines in rapid succession, that premium buys you brand prestige and little tangible performance gain.