Gun Review: HK MR556A1

    Alright so it is no secret that I am an H&K guy, and if you have followed my previous articles then you can definitely see that I have taken a liking to them over the years. Hell, the US Government will not let H&K import modern sporting rifles due to the ’89 import ban so I went out of my way to build a semi-automatic G36 clone out of an SL8 and even a title II UMP want-to-be out of a USC carbine. That being said, it came as a shock to me when I got selected to review the new H&K MR556A1. You see, the way us writers get selected to review products (when it comes to firearms) is done by rotation rather than intentional selection so I was thrilled when I got the word. I was also pleasantly surprised at how easy H&K was to deal with; I got in touch with a delightful H&K employee via e-mail and she had a shiny new MR556A1 rifle at my FFL within a week.

    Now let me say this; I have damn near every H&K firearm that has ever been made available to non-SOTs in the USA but this is one gun even I thought I would never own. I figured it was just another piston driven AR variant with some bells and whistles and those wonderful two red letters than add a grand onto the price tag but I wanted to give the rifle the benefit of the doubt and try to put my pre-concieved notions aside to make this test as objective as possible. I am also not a big AR15 guy. I believe the platform is versatile and makes the most sense out of all the semi-auto .223 rifles out there to own due to parts availability, price, and a slew of other reasons but over the years I have quite simply grown bored with the platform. I have seven or eight of them sitting in my safe, but I honestly cannot remember the last time I have shot one of them. Regardless, I was still excited to hit the range with this new AR that is all the rage among special forces groups across the globe and is even slated to replace the M249 as a squad automatic weapon in some US military units (in a heavy barreled variant). So lets get to it.

    In the box you get the rifle, an HK magazine (these are built like tanks), lock, manual, pin tool, multi tool, and some HK swag. The rifle comes equipped with the H&K diopter sights, which are a rotating drum and fixed front sight. So I loaded up my vehicle with the HK and some Privi Partisan 55 grain ammunition and got to it.


    So after shooting a few shots I noticed that I was hitting several feet (not inches mind you) low. I went to my range bag to grab my handy-dandy H&K sight tool and noticed I did not have it on hand (d’oh). Oh well, that was not going to impede my progress. I took the ACOG off of my AUG and threw it on the MR556A1 to continue the accuracy test.


    So I continued shooting sitting down with no rest or bags (I like shooting freehand) at 100 yards.


    I shot five groups of five rounds like this and here is the best group:


    And my worst:


    So with PPU 55 grain ammo I averaged 1.26 inches at 100 yards. I am sure with bags or a rest I could have shot a consistent 1 inch group or better, but it doesn’t matter I suppose as this little accuracy test was acceptable. I spent the rest of the day shooting steel targets at 100 and 200 yards and shot six 30 round magazines for a total round count of 180. So accuracy is acceptable and I believe any AR15 worth its salt should be able to perform at least this well.

    But how about reliability? Well, luckily every Saturday after the 4th of July I attend a local machine gun shoot (there is no better way to celebrate the independence of your country than by destroying a small part of it) and I got a chance to beat on this gun hard. I also corrected the sights and got the irons on target. So for a test of reliability I got twenty 30 round magazines (600 rounds) and fired them all back to back letting the gun rest only to hand off to other shooters. Mind you I told everyone to beat on it, rapid fire it, bump fire it, etc:




    The HK chugged along and ejected each round perfectly and consistently to 3:00. The oil on the gas system burned off but that was the only smoking to note and the bolt carrier was reasonably cool to the touch (I had to verify that video where the HK rep fired a bunch of rounds on full auto then handed the bolt carrier off to someone else). So after this I had a well broken in HK MR556A1 and a pile of various spent magazines:


    So it didn’t jam and I asked everyone who messed with it what they thought and if it felt any different than a DI AR15/M16. The general consensus was that the recoil impulse was unique and that it was comfortable to shoot, but nothing was super amazing or spectacular (I agree with what they said by the way). However a short 600 round torture test with no jams and minimal heat buildup was something I thought was pretty cool.

    So it was time to clean the HK MR556A1. It is well known that piston guns run cleaner than a DI gun, but I wanted to see how much buildup there was. I put on a pair of new white inspection gloves (I keep a big bulk pack of them around for handling valuable firearms) to see how dirty the bolt and carrier got. I was shocked at the lack of buildup. First I had to use the tool located in the stock to open the gun up and pull the carrier:


    I then prepared to wipe the carrier from the bolt to the back in one swipe with an inspection glove:


    And this is all that was there after 780 rounds:


    I must say that I was shocked. After a range outing with a 6920 or other DI AR variant the gun would be this dirty after a magazine or two.

    So I thought I might use the rest of my glove to grab the carrier and wipe it all the way down:


    After generously wiping the carrier down by hand my glove looked like this:


    Nearly 800 rounds and that is all the glove showed, and gloves don’t lie (unless you are OJ Simpson I guess).

    So the cleanliness of the carrier is a result of H&K’s short stroke AR18 derived gas system:


    One thing I noticed is that the actual piston tappet is a G36/SL8 carry over, however the rest of the system is slightly different. I must say this system is quite astonishing and I have no complaints other than it adds weight to an already heavy rifle.


    So there you have it, but now for my bullet points:

    The Good:

    • As accurate as any other 16″ barreled AR variant I have played with
    • Very comfortable gun to shoot with a light recoil impulse, even for an AR
    • I like the diopter sights a lot, some may not
    • Cleaning this gun takes two or three patches and a bore snake
    • 780 rounds, no cleaning, no jams so the thing is reliable
    • Full length rail system and front quad rail
    • Tons of storage in the grip and stock
    • Upper and lower are incredibly tight
    • Flared magwell
    • Upper will fit other AR lowers

    The Bad:

    • The rifle weighs 8.6 lbs
    • An HK sight tool is not included
    • The bore is not chrome lined (HK says for accuracy)
    • Will not suppress as well as a DI gun
    • Will not take pre-generation 3 p-mags
    • The bolt carrier is milled to prevent full auto function
    • The chamber has an odd extention to prevent the install of a 416 bolt
    • An RDIAS or Lightning link will not work (no fun switch for you) without serious work

    The Ugly:

    • The MR556A1 rifle is priced at $3,295
    • $3,295 is a lot of money
    • $3,295 for an AR variant is just… damn (this coming from an HK guy)


    So all in all for the price of $3,295 I would pass on the MR556A1. Yes, the rifle shoots well and is reliable, but unless you are a serious collector or just have to have what some consider the absolute best then pass on this gun and buy a much cheaper piston AR. If the price point was closer to $2,000 I would be a buyer but on popular auction sights these are going for $3,500 so obviously people are biting. IMO if you live in a free State then put that money towards a machine gun for investment purposes, and if you don’t then plop that cash down on your mortgage!

    Alex C.

    Alex is a Senior Writer for The Firearm Blog and Director of TFBTV.