HK MR556A1

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HK MR556A1

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A direct descendent of the HK416, the MR556A1 is a semi-automatic rifle developed by Heckler & Koch as a premium level commercial/civilian firearm with match rifle capability. Like the HK416, the MR556A1 is a major product improvement over conventional AR-type carbines and rifles. The MR556A1 uses the HK proprietary gas piston operating system, employing a piston and a solid operating pusher rod in place of the gas tube normally found in AR15/M16/M4-style firearms. This method of operation virtually eliminates malfunctions that are common to direct impingement gas systems since hot carbon fouling and waste gases do not enter the receiver area. This is the same key feature critical to the success of the HK416 rifles used by leading military and law enforcement customers. The MR556A1 is produced in the USA using American and German made components. The MR556A1 uses many of the same assemblies and accessories originally developed for the HK416. Like the famous HK416, the MR556A1 uses a German-made barrel produced by Heckler & Kochs famous cold hammer forging process. The highest quality steel is used in this unique manufacturing process producing a barrel that provides superior accuracy and long service life. But unlike the HK416, the MR556A1 does not use a chrome-lined barrel. Chrome-lining can sometimes mask bore imperfections and negatively affect accuracy. For the new series of Heckler & Koch semi-automatic MR rifles, HK designers and engineers believe best accuracy comes with an unlined bore. The unchromed barrel has an internal profile of 6 lands and grooves with a 1 in 7 inch (178 mm) twist. It is also moderately swagged with a slightly smaller internal diameter at the muzzle end than the chamber end. This feature has a positive effect on bullet accuracy and velocity. The thick, heavy contour 16.5-inch MR556A1 barrel also contributes to its excellent accuracy. A precise enhanced two-stage trigger adds significantly to the accuracy of the MR556A1 and an extended latch charging handle makes operating the rifle with a telescopic sight easier. The retractable buttstock can be locked into a solid, non-moving position by tightening an Allen screw in the bottom of the stock. Special target rifle takedown pins ensure the upper and lower receivers are firmly mated for accurate performance. Designed to function with a wide variety of high quality 5.56 x 45 mm ammunition, the MR556A1 uses a C.I.P. dimensioned chamber (a chamber with dimensions specified by the Commission Internationale Permanente).The MR556A1 also functions reliably with most quality Caliber .223 Remington ammunition. The MR556A1 is being produced with the same commitment to quality as German-made HK firearms. By using joint U.S./German manufacturing, Heckler & Koch leverages the relative strengths of two continents to make the preeminent AR-type firearm, combining the designs innovations of the USA and Germany into one new product.  *NOTE* rail system may differ from the one pictured.

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HK MR556A1 Specs

2 Category

Technical Data


.223 Remington (5.56x45mm NATO)









Barrel Length

16.5 "

HK MR556A1 Features

The HK MR556A1 is what you get when you ask German engineers to improve the AR15 since they won’t make a civilian copy of the MP7.  Derived from the HK 416 (M27) rifle, the MR556A1 is a semi-automatic, civilian-legal semi-automatic rifle that operates on a short-stroke gas piston and multi-lug rotating bolt action.  Often misidentified as an AR15, this HK rifle shares almost no common parts and has many functional and ergonomic improvements.

HK MR556A1 Ballistics

.223 Remington (5.56x45mm NATO) Ballistic Data
Range (Yards) Drop (inches) Velocity Energy Wind drift (inches) Time (milliseconds)
0 0 0 0 0 0
50 0 0 0 0 0
100 0 0 0 0 0
150 0 0 0 0 0
200 0 0 0 0 0
250 0 0 0 0 0
300 0 0 0 0 0
350 0 0 0 0 0
400 0 0 0 0 0
450 0 0 0 0 0
500 0 0 0 0 0

HK MR556A1 Capacity

The HK MR556A1 is chambered in 5.56x45mm NATO (.223 Remington) and feeds from all STANAG-compatible magazines.  This gives the rifle the ability to accept double-feed box magazines with capacities of 5, 10, 20, 30 and 40 rounds as well as allow it to accept 60 and 100 round quad-stack and drum magazines.
With an overall length between 34 and 38 inches depending on the placement of the adjustable stock, and with an unloaded weight of 8.6 pounds, the MR556A1 competes in size against standard AR15 pattern rifles but definitely has a rather excessive weight.  This is due to the slightly larger receivers, thick aluminum handguard, improved gas system and heavy-profile barrel.  While some may be swayed by the added weight, the components’ added weight delivers a softer recoil impulse and greater accuracy.

HK MR556A1 Mobility


HK MR556A1 Ergonomics

The MR556A1 has a rather large 12-inch free-floating handguard that offers a very beefy grip and has a raised full-length optics rail that gives a much better cheek weld.  The fire controls are set up the same way as the all-too-familiar AR15 with the inclusion of an ambidextrous safety, and the adjustable stock allows the user to adjust the length of pull to accommodate for differing user heights as well as any range gear.

HK MR556A1 Fit & Finish

The HK MR556A1 is built on a forged receiver set with an upper receiver that has had its front face lapped to ensure a perfect barrel fit for peak accuracy.  All contacting surfaces are honed or polished for an impeccably smooth action, and the short stroke gas system keeps the bolt group much cooler and cleaner than rifles that operate on the standard internal piston action.

Fit and Finish

HK MR556A1 Comparisons

How much is a HK MR556A1 worth?

In 2024 a new or used HK MR556A1 value varies depending on supply and demand. In the last 12 months there is great demand for a HK MR556A1 and most rifles. The Price for a HK MR556A1 has increased in cost by $0.00 in 2024 compared to 2023.

Estimated New and Used Values for a HK MR556A1 Values are based on a basic model with no options or colors.

Condition Trade-In Private Party Dealer
New In box $2,054.10 $2,686.14 $3,160.16
Excellent $1,896.10 $2,528.13 $2,844.14
Very Good $1,738.09 $2,528.13 $2,844.14
Good $1,580.08 $2,370.12 $2,686.14
Fair $1,106.06 $2,054.10 $2,528.13
Poor $790.04 $1,580.08 N/A

Gun Value Conditions explained:

New in box - 100% condition in unopened box. Excellent - 95%+ condition with or without box.

Very Good - 90% - 95% condition (all parts/finish should be original).

Good - 80-90% condition (all parts/finish should be original).

Fair - 30% - 80% condition, parts, and finish may or may not be original. Must function properly and shoot.

Poor - under 30% condition. Firearm has severe wear and tear, does not function, or is damaged.

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