Gun Reviews


Posted Jun 16, 2023
Cover Image for HECKLER & KOCH MR 556 A1

The Heckler & Koch MR556 A1, produced by the legendary German firearms maker, is one of the most popular and sought-after modern assault rifles on the commercial market. It’s revered for its quality construction, its sleek design, and its suitability for a variety of tactical uses. Heckler & Koch designed the MR556 as a cutting edge solution for today’s tactical and competitive shooters, and it has based its foundation on the time-tested success of the G3 battle rifle and the classic HK416.

Let’s begin by taking a closer look at some of the features that make the MR556 A1 stand out from other rifles of its class. Firstly, the rifle utilizes a piston-driven operating system. Unlike conventional gas-driven systems, the gas piston system on the MR556 is much cleaner, reliable, and less prone to malfunction than traditional impingement systems.

Another innovative feature of the MR556 is its Nickel Boron coated bolt carrier group. This allows the rifle to operate with extremely smooth and reliable cycling, while also providing improved lubrication and higher corrosion resistance.

The MR556 A1 also comes equipped with outstanding adjustable stock. This is especially helpful for shooters in need of a rifle with more adjustable features than the average mil-spec or tactical model. A length of pull adjustable by up to four inches, as well as a cheek rest that can be raised or lowered independently, allows a shooter to customize the fit of the rifle to his or her specific needs.

The MR556 also features an improved trigger guard that can accommodate gloves or other forms of finger protection, a full-length Picatinny rail system for mounting optic and other accessories, and a machined one-piece upper receiver which provides a scaled-down design for reduced weight and improved balance.

For those interested in customizations, the MR556 A1 allows for an array of aftermarket options that make this more of an individual, customized firearm. Everything from different barrels and triggers to muzzle brakes and stocks can easily be switched out, making it a perfect choice for anyone looking to create their own custom rifle.

The flip side, however, is that these time-tested features come with a hefty price tag. While Heckler & Koch have managed to keep the cost relatively low compared to other rifles in its class (especially when compared to the HK416, which it is based on), it still is a significant investment for most shooters.

When it comes to performance comparisons, the MR556 A1 has come up short when compared to the more expensive and advanced offerings of its competitors, such as the SIG Sauer 516 and Bushmaster XM-15. While these rifles have provided slightly more reliable performance when subjected to rigorous testing, the MR556 A1 still holds its own against these weapons.

When firing from the bench or prone, the overall accuracy of the MR556 A1 has been impressive. The 5.56mm round combined with the rifle’s piston-driven operating system is able to provide impressively tight grouping even at extended ranges.

In addition to accuracy, the barrel length of the MR556 A1 also allows for increased velocity, which can make it suitable for long-range engagement. Heckler & Koch have worked to reduce the rifle’s muzzle climb, which can cause a loss of accuracy when firing rapidly, by adding a more ergonomic design and better distribution of weight.

Overall, the MR556 A1 has been an impressive and dependable rifle. It’s popularity among tactical shooters and competitors alike is a testament to its reliability and quality. And while it may not hold its own against the more advanced offerings of its competitors, it still stands as an impressive and affordable modern assault rifle.

Pros & Cons


  1. Reliability: The HK MR556A1 is one of the most reliable AR-15 rifles available, thanks to advanced engineering and solid construction.
  1. Accuracy: The Mr 556A1 is extremely accurate, with the capability to hit distant targets with ease.
  1. Durability: The HK MR556A1 is built to last, with its high-end parts and advanced technology keeping it running in even the toughest conditions.
  1. Adjustability: The HK MR556A1 is designed to be customizable, with adjustable stocks and a variety of attachments.


  1. Cost: At its current retail price, the HK MR556A1 is one of the more expensive AR-15s on the market.
  1. Weight: At 8.6 lbs, the HK MR556A1 is a heavy rifle, making it unsuitable for long range deployments or carrying in the field.
  1. Ammunition Preference: The HK MR556A1 will function best when using 5.56x45mm NATO ammunition.

Who Should Buy

The HK MR556A1 should be considered as a premium rifle for those looking to participate in high-level competitions or for serious defensive purposes. As such, the MR556A1 is best-suited for experienced shooters who have the necessary skills, training, and discipline to use a rifle in a safe and responsible manner. As the cost of the rifle is fairly high, it may not be the best choice for those on a budget or those who are inexperienced. Additionally, due to the weight of the MR556A1 and its full auto capabilities, it is not recommended for hunting.

Caliber5.56 NATO5.56 NATO308 Win7.62 x 39mm
Operating SystemGas PistonGas PistonDirect ImpingementLong Stroke Gas Piston
Barrel Length14.5 inches13 inches16 inches16.5 inches
Magazine Capacity30-round30-round20-round30-round
Weight7.6 pounds8.7 pounds8.2 pounds8.2 pounds
Length (Stock Retracted)32.5 inches28.25 inches32.25 inches36.5 inches

Features / Specs

•Caliber: 5.56 x 45 mm

•Operation: Gas operated, rotating bolt

•Barrel: Cold hammer forged, chrome lined

•Weight (empty): 9.36 lb (4.25 kg)

•Barrel length: 16.5 in (420 mm)

•Overall length: 34.8 in (885 mm)

•Stock: Fixed telescopic stock or 5-position telescopic

•Rate of fire: 700 – 900 RPM

•Muzzle velocity: 2,925 – 3,250 ft/s (892 – 991 m/s)

•Sight radius: 16 in (409 mm)

•Effective range: 492 ft (150 m)

Popular Accessories
  1. Magpul Forend with Angular Light Mount
  1. Magpul Angled Fore grip
  1. Flashlights or Lasers
  1. Sling
  1. Red Dot Scope
  1. Bipod
  1. Flip-up Sights
  1. Suppressor
  1. Hogue Grip
  1. Extended Magazine Release


The HECKLER & KOCH MR 556 A1 is highly regarded for its accuracy. At distances of up to 300 meters, the MR 556 A1 is able to maintain a high level of accuracy. The rifle's cold hammer-forged barrel ensures precision shots, and its diopter rear sight provides a clear sight picture for improved accuracy. The 5.56mm NATO caliber round is known for its accuracy and the MR 556 A1 has an exceptional rate of fire for its caliber. Tests by users and shooting professionals have found that the MR 556 A1 delivers reliable shot grouping when fired, often less than 1 inch at 100 meters with militarily issued M855 rounds. The combination of reliable ammunition and precise construction results in an exceptional accuracy with a .223 Remington or 5.56 Nato. Overall, the MR 556 A1 is a highly accurate choice to meet the needs of any shooter.

Video Reviews
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Angry Lady Heckler.
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Comedians vs DUMB HECKLERS

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