Ruger SR-556

The increasing interest in the AR-15 series of rifles and…

The increasing interest in the AR-15 series of rifles and carbines has created a controversy whether the AR should have a gas impingement or gas piston operating system. While the AR certainly stumbled in its early days, its system has certainly been perfected, but it does require consistent maintenance to keep it operating properly.

The largest criticism is how the direct gas system blows debris from the fired cartridge back into the operating system, primarily the bolt, which collects to the point that it can actually slow the action or stops the gun completely. Admittedly, this would take a while, probably in excess of a thousand rounds on a well-made gun, which would not be a problem for the legally armed citizen or law enforcement officer, but for the soldier in a battlefield situation it is certainly problematic.

ruger2The obvious solution is to make sure that the dirt generated by the firing cycle never makes it into the action in the first place, which is why many knowledgeable folks advocate the gas piston action for the gun. This action is similar to the gas impingement but with an important difference — the gas created by the fired cartridge pushes a spring-loaded piston back toward the gun’s action and strikes an “anvil” attached to the bolt where the gas key was originally located.
This striking action cycles the bolt and keeps debris far away from the inside of the receiver. Sounds like a great idea, right? It is but the problem has arisen in the application of the system with some of the gas piston systems used to “upgrade” the AR being a bit small and fragile, and eventually breaking down with usage. Trying to retro-fit a gas impingement gun under standard handguards requires components that are sized to fit existing space, thus many such systems are not as robust as they should be.

The obvious answer is to build the gun from the ground up to work as a gas piston gun and to build the parts robust enough to stand up to the constant pounding the gun must take in order to depend one’s life on. Ruger has done this with the introduction of their new SR-556 model, and like all things from Ruger, it is built like a tank. Interestingly, Ruger has been making AR components for many years but this is their first entry into the AR-15 market and it looks to be a good one.

Gun Details
The SR-556 offers Ruger’s proven ruggedness and reliability while changing the AR-15 platform to a piston driven system. The gas piston driven SR-556 runs cleaner, cooler, and is easier to maintain than gas impingement rifles, offering significantly improved reliability due to the reasons offered earlier. The patent-pending two-stage piston driven operating system in the new Ruger SR-556 provides a smooth power delivery stroke to the action and vents combustion residue out of the bottom of the gas block.

ruger3When asked why Ruger decided on this system instead of a traditional gas impingement system, Product Manger Mark Gurney stated, “It’s a new gun, why go with an old system?” Makes sense. The four-position adjustable gas regulator allows the shooter to tune the rifle to specific ammunition and rifle conditions, minimizing recoil while maximizing reliability and long-term endurance.

Ruger’s Media Director Ken Jorgenson told me that the level of adjustment could be determined by where and how far the brass is ejected from the gun. A one-piece bolt carrier further enhances reliability with an integral transfer key that is also chrome-plated for enhanced reliability and quicker cleaning. Designed for long-lasting accuracy, the heavy contour, 16.12-inch chrome-lined barrel is cold hammer forged from Mil-Spec 41V45 Chrome-Moly-Vanadium Steel. The barrel has a 1-in-9-inch twist rate and is capped with an AC-556 flash suppressor giving the SR-556 a distinctive Ruger look.

The SR-556 is chambered in 5.56mm NATO, thus the Ruger SR-556 will also fire .223 ammunition with complete safety and reliability. A one-piece 10-inch Troy Industries Quad Rail Handguard provides ample room for mounting sights, optics and other accessories and is made exclusively for Ruger. This SR-556-specific handguard is pinned to the upper receiver for added durability and provides a rigid mount for the piston driven transfer rod.

The SR-556 is also equipped with Troy Industries Folding BattleSights, which will keep them out of the shooter’s field of view when enhanced optics like a Trijicon ACOG or Aimpoint red dot sight are used. These rugged, high-quality sights co-witness with Mil-Spec optics, and are easily removed or replaced. The sights can also be folded down with the push of a button or quickly flipped up with your thumbs.

The windage adjustable rear sight includes an instantly converted short and long-range aperture, and the protected front sight is elevation adjustable. I asked Mark Gurney why Ruger opted to go with such high-end accessories and was told, “We needed a specifically built forend to house our gas piston system and since we wanted to offer our customers a truly unique gun, we opted for the best we could find.” In addition, the Ruger SR-556 is equipped with a six-position telescoping M4-style buttstock that houses a Mil-Spec buffer and spring. A Hogue Monogrip pistol grip and three Troy Industries Rail Covers provide a comfortable and ergonomic grip when carrying or shooting.

Long life and performance of the SR-556 is enhanced with the use of high-performance finishes, which deter corrosion and add lubricity. The barrel and gas block are chrome lined, while the bolt, bolt carrier, and extractor are hard chrome plated. This makes cleaning these areas much easier and quicker as well as aiding reliability.

ruger6The flash hider and the exterior of the barrel, gas block, and regulator are manganese phosphate coated for added durability and a business-like appearance. While some may desire a traditional AR-style bird cage flash hider, I believe the Ruger Mini-14 version gives the gun a distinctive Ruger look that separates it from other similar rifles. Todd Wilkinson, Chief Engineer-Rifles, who was deeply involved in the gun’s design, told me that this was the exact reason they opted to use their proven flash hider.

All of the aluminum parts used in the gun’s construction are Mil-Spec hard coat anodized. The SR-556 is supplied with three, 30-round Magpul PMAG magazines that are some of the most reliable magazines ever built. The demand for PMAG’s is quite high and Ruger made a good choice in using these quality pieces of kit. These durable and lightweight magazines feature a storage/dust cover, a stainless steel spring, and a self-lubricating, anti-tilt follower for enhanced feed reliability.
The flat top upper receiver and barrel assembly are specific to the Ruger SR-556 while the lower receiver is built with Mil-Spec components including a single-stage trigger. The lower receiver is compatible with AR-style magazines, grips, buttstocks, and trigger assembly components so aftermarket products can be used to better fit the end user. The Ruger SR-556 comes from the factory in a quality padded carrying case that features the Ruger logo, hook-and-loop fasteners to stabilize the rifle within the case, and internal magazine pockets.

Range Time
Like any product designed to perform, features and looks are one thing, but it’s how the gun runs that is important and the first thing we need to know is how accurate the gun is. To find out, I contacted Leupold and had them send one of their scopes from the MR/T series, in this case a 2.5-8×36 Mark 4 model.
This variable power scope would give me both up close capability as well as some “reach” for targets at greater distances. More and more serious operators are selecting variable power optics for their individual long guns just for this purpose. The greater versatility that can be placed into any weapons system, the more potential situations it can handle. Since .223 ammo is becoming more and more scarce, I opted to sight in the SR-556 with common FMJ ammo. As luck would have it, I was able to get the gun zeroed in 10 rounds and was able to perform an accuracy test.

ruger5Accuracy was tested at 100 yards from a bench rest using five rounds of various ammo styles. I was interested in seeing just how much bullet style and weight would affect accuracy, so I used everything from 53 grains up to 77 grains.

In all fairness, I must advise the reader if it were not for my loss of concentration that the super-accurate Federal BTHP would have posted a sub-MOA (minute of angle) group with four rounds clustering into a 0.75 of an inch hole. After seeing how well I had shot the first four rounds, I committed the rookie mistake of becoming overly excited and lost focus on the last round with the resulting single flier. One is never too old to continue the practice of fundamentals.

This being said, the SR-556 proved to be exceptionally accurate with all of the loads tested regardless of weight, manufacture or bullet style. Over the years I have seen a number of guns that preferred one style of bullet over another meaning that one needed to find particular ammo in order for their gun to perform its best, but this was not the case with Ruger’s new rifle as it worked equally well with all loads tested, posting near MOA performance when combined with the excellent Leupold optic.

During testing of this two-part gas piston system, thousands of rounds were fired without cleaning and without failure. The piston driven transfer rod is electro-less nickel/Teflon-coated, which adds lubricity to the parts that do build up a great deal of crud as the rifle is fired. Yes, the bolt assembly remains relatively clean, but the gas piston components foul quickly with the dirt and grime that are expelled as the cartridge is fired. No gun runs clean so expect to scrub these components at some point. This being said, I believe it is safe to say that any AR will stop running due to a fouled bolt assembly before a fouled gas piston but only time will tell.

I continued to test the SR-556 for the remainder of the day, performing a number of combative carbine drills and basically getting in a solid practice session with the new gun. Since I was at my gun club, a number of folks happened by and noticed that I had something different and begged me to shoot the gun.

While it was a bit hard on my dwindling ammo supply, I let everyone who asked take a run at it. At the end of the day, the SR-556 had digested over 1,000 rounds without a single “burp,” and with a barrel and action that was cool to the touch. Everyone who shot the gun had nothing but good things to say with the normal follow-up questions being “How much is it?” and “When will it be available?”

ruger8While testing the gun, I added several components that I felt enhanced its performance. The first was the new short quick attach forward grip from Ergo Grip and the second was the CTR stock from Magpul. While vertical forward grips are controversial I have found that having one gives me greater control of the muzzle as I move from target to target. The secret to using such a grip is not to grasp it like a beer can, but to keep the thumb on the outside and “cam back” just as you would if the hand were being used as support on a pistol.

The Magpul CTR is a superior adjustable stock as it locks solidly in place, offering as locking lever that removes any and all stock wobbles. The rubber buttpad is not used to tame the recoil of the 5.56, but keeps the stock from “walking” on the shooter’s shoulder in rapid fire. Both are worthwhile additions to any AR platform.

Final Notes
At the conclusion of a week of shooting the SR-556, I came away with a very positive opinion of the new gun. Did I have any druthers? Sure, I would like to see a budget model for those who want a basic carbine without all of the rails and other gizmos. While Troy Industries makes a terrific product, many people can get by with less and would appreciate the reduced cost. The folks at Ruger assured me that this is being considered.

With the demand for AR-15 weapon systems continuing to increase, I believe that Ruger will sell all of these that they can make and for good reason. It is a robust, solidly built, well thought out rifle that would be a good choice for the Special Forces Operator, law enforcement officer or the legally armed citizen. It is that versatile!

Load Comments
  • Gary Eden

    Got one , but would like it outfitted just like the photo. Beautiful. Any info?

  • josh henry

    i am a rugar owner and have to say it is great advise the purchase ran about 5000 various rounds through the gun without cleaning or oiling and it puts them down range fine barrel is still clean but piston was tarred up

  • josh henry

    purchased the ruger, great gun, wish it had a lighter trigger pull,and also doesnt run too well with tull ammo seems the cartrige wants to stick in the barrel other than that its a great choice and advise any ar lover to purchase.

  • Steve Wilson

    @James Dotson

    DGI rifles are “good” but don’t get let our tightwad military fool u into thinking “ANY” DGI rifle compares to the SR556’s reliability. I’m in the military too and I say those DGI’s should have been scrapped decades ago. Ive had my SR556 for 13 months now. Fired about 15,000 rounds and have NEVER cleaned it, NEVER oiled it, and there’s NO worn or damaged parts. Yea u heard me NO damage what so ever to ANY moving part, and NO wear to the buffer tube. You shouldn’t have to break down and clean a battle rifle after every use (DGI). DGI rifles are cheap and they get the job done. That’s why the military uses them. NOT because they are top of the line. If the military wasn’t so cheap they’d have just given us all M14’s! Stop living in the past. The future is here, and it’s here to stay!

    Ruger’s #1 Fan

  • Dennis

    I love my Ruger SR556, it is hands down one of the best made AR rifles out there. I have put more then 500 rounds through it and with no problems at all. This rifle is also very accruate and is a joy to shoot. I know that people complain about the price but buy one and you will know that the rifle is worth every penny. Every time I take the 556 out of the case at the range everyone wants to look at it. Ruger got it right with this AR and the only thing negative I might add is that it is heavy compared to cheaper rifles that you might compare it to. For me this is not a negative because there is less recoil and it makes getting on target for a the next shot easier and faster.

  • James Dotson

    @Enzo Not quite sure you are referring to when you say “the military no longer uses them [DGI].” I am deployed to central Iraq at the present and have a DGI M16 and an M9, along with everyone else here on COB Adder in Talil/Dhi-Qar, Iraq. I don’t know a single person here who doesn’t have a DGI rifle, though I am sure the Special Forces guys on the other side of base use piston-driven rifles. DGI will continue to be issued and used for general military service. And if you had read early reviews of the HK416’s used in Afghanistan in 2009 and 2010, many users reported the pistons seizing/failing during cold temperatures, though many of those problems have been fixed. Even master [AR-15] rifle maker, John Novesk, said piston driven rifles are generally pointless, fixing a problem that doesn’t need to be fixed in the first place. Why spend the extra money on a Ruger where after 5,000 rounds the buffer tube falls apart and fails when you can spend the money on a new DGI rifle that survives a 33,000 round torture test with zero failures. Both rifles have pros/cons but neither are superior to one another. Brush up on your facts, because you obviously don’t know what you are talking about when it comes to military service rifles and DGI.

  • Enzo

    @ Vik – the DGI AR is NOT reliable. That is why the military doesn’t use them anymore and are looking to dump the M4 too.

  • scott

    Loading issue idea. Make sure you are not loading 31 rounds. The last round will inhibit the ability of inserting a mag with the bolt forward. I’ve had noooo issues. 500 rounds down. Bout it 2 weeks ago. Got a reflex on top.. looking for front foregrip.

  • David

    Jay, I wondered the same thing about the 4 small velcro straps. I’m guessing it’s there to secure an extra barrel or cleaning kit? Not much room for anything else at the bottom of the case.

    First time shooting my new 556E model last night. Used a cheapo Barska 3-9×42 scope and was very impressed with the gun. Not so much with the scope, but it’s what I had laying around. Anyway, at 50yds was putting 3 shot groups together that I could cover with a quarter. Although it was getting dark and I couldn’t see the center circle on paper at 100 yards, I could cover the 9 shot group with my hand. Not too bad with cheap scoope and 55gr. value pack Federal ammo from Wally World. Was using sand bags on a concrete shooting table so accuracy should have been pretty good. I did notice toward the end of the session when I picked up the rifle to do some unsupported firing that the front hand guards were very hot. E model owners will need to buy the rail covers if you plan to do any tactical style shooting.

  • Dr. F

    Hey, Jay Stone, the 4 Velcro straps in the soft case are used to hold the SR-556 in place. The barrel end of the soft case is the end with the two magazine pouches.

  • Jay Stone

    I purchased a Ruger SR556 from Impact Guns, Roy Utah. The box had been opened and upon inspection of the gun and the parts that was included once I brought it home, there are 4 velco straps down the center of the inside of the soft case, what would that be used for, and was something supposed to be included. I would like to ensure I recieved all the items that should be included with this purchase.

  • Seth

    jon Says:
    September 11th, 2009 at 8:26 am
    What laser is used in the picture? Thanks!

    Jon its a Laserlyte K-15 Kryptonyte Green Laser. You can buy them on for about $249.95.

  • Jason B

    My wife bought me the 6.8 SPC version as well for Christmas. I have to say, I love this rifle. Being in the military, I’m used to the old AR gas system and how dirty the bolt and receiver get. After firing this rifle, the bolt and receiver only needed a good wipe down and a little CLP. The only issue I had was that the mag’s had to be slapped hard with force to seat firmly, but it’s getting better with break in time.

  • Aron Braksma

    The Ruger SR-556 is a heavy duty platform! Mine fires everything without a glitch – M855, SOST MK318, and Herter’s steel cased ammo without a hitch, plus is much easier to clean than DI guns. The trigger pull is heavy, but it still shoots near MOA. In addition to my usual toys, I’ll add a VLTOR modstock, a new trigger, and have an AR that will challenge POF Armory or LWRC for much less cash. Ruger knocked it out of the park with this one!

  • Rick

    I fired over 1500 rounds of different brass cased ammo through my sr556 with no ammo issues of any kind. However this rifle does not like cheap steel cased ammo at all. Not a problem for me since I don’t like to fire cheap Russian through guns I like. As for carrier tilt there were signs of it rubbing early on so I switched to a PWS buffer tube and it has not been an issue since.

  • Jeff

    My wife gave me the 6.8 version of the 556 for Christmas. It is very nice. I have been hunting deer with my first 6.8 for a couple of years and really like the caliber. It is easy to reload and performs very well out to 350 yards. Now I just have to decide what scope to put on the 556.

  • rsh

    Got my SR-556 back from the factory and I must say Im impressed with Ruger customer service. They put a brand new barrel on my rifle. Works great now and they had it back to me in about a week and a half. If you have a problem with your Ruger just call them and be nice and they will make it right for you!

  • Paul

    Anyone have the 6.8 SPC version? I’ve been researching AR style rifles for a few months now and after talking to many experts I’m going to go with the SR-556 in 6.8 SPC.

  • rsh

    Ive had this rifle for about 7 months. It shoots very well but I believe mine has a rough chamber that I didnt notice till I tried to fire it with the gas setting on 0. Its almost impossible to manually eject the spent case or a live round. This is a dangerous condition to have. I then noticed all kinds of scratches and an indentation in identical spots on the spent brass. Called Ruger and after a little discussion Ruger had it picked up today by UPS. Also sent some spent cases back like they asked so they could examine them. Ill see when it comes back how good their customer service is. I really like this rifle and hope they get it straightened out. Other then that the rifle has had close to 1000 rds through it without a burp when fired in semi-auto mode. Im very happy with it and want it back a quickly as possible 🙂

  • Dennis Breece

    This gun has an ammunition feed problem. Buyer Be Aware!!

  • Jared

    I’ve put about a thousand rounds through my SR-556 and had only two “burps”. Both times it was the poor quality ammo. Any Federal or Winchester ammo goes through just fine. Also, I barely have to clean it. I’ve only cleaned the piston once and it wasn’t even necessary for proper functioning! Everything else just wipes clean. Amazing.

    One thing to watch out for is that, during hot days with fairly fast firing, the front end really heats up. Even touching the rails without gloves was HOT. The rail covers prevented any discomfort while firing though. Just make sure you don’t touch the exposed rails!

    Everyone who has fired my SR-556 has just looked in awe and said “I want one.” It is indeed that awesome. If you get a lemon, as can happen with any product, just send it back to them and Ruger will fix whatever the problem is.

  • don

    I think this rifle needs a slightly longer barrel for sub moa average, a choice of target butt plate,carbon fiber (no rail except on piston block for iron sights)…this would be an excellent rifle for your match team. And, an excellent rifle for military/LE needs at 400-500yrd shots. The cooled down carrier group should add alot of life to those parts! That would be the most sellable upgrade yet. Good going Ruger on this new platform.

  • Todd

    Ryan, what is wrong with your rifle? Eric, the magazine should go in nice and easy. When you pull the charging handle back is when you need the be aggressive. Pull back and let go quick. The rail cover slide on and you press the tabs in. It has to be lined up in the grooves of the rail.

  • Larry Hazelwood Jr

    This Gun is amazing. Ruger has set a new bar in the AR world and I am glad to say I truly think that the AR belt is back in the USA..

  • Roger OD

    Sweet Rifle! Smooth. Had to adjust the valve to posistion #2 to push some 55gr Wolf down the tube. No problems either way. Very stable platform. I have 3 other AR platforms, the SR556 is now my favorite.
    Get one. You will be amazed.

  • Rod

    How do you attach the rail covers that come with the rifle.

  • Bob Curtis

    How is the heck to you attach those rail guard covers that come with the rifle?


    Just picked mine up and it is GREAT. Forget the haters and get one, they can stick to their Stags and UTG after market parts if they like……

  • Ryan

    Trying to find the vertical foregrip in the photo. I’ve searched high & low. Doesn’t match anything that Ergo Grip offers. Any help would be greatly appreciated. By the way. Your article was a great resource in my decision to buy an SR 556. Thanks.

  • Nick

    I’ve had my 556 since December and have almost 15000 rounds through it only 1 misfire on reloaded ammo. Greatest gun I own I have several RRA and bushmasters. By the way Ryan, forget the S&W it’s made by Stagg arms and stamped S&W and cost $400 more. Buy a stagg T2 if you don’t like the ruger and really save some dough. Gun operates flawlessly with any ammo in all weather conditions and the EoTech on top makes it a great CQC weapon. Highly recommended to future AR buyers.

  • Eric

    Love this gun it is very smooth with little recoil.
    My only complaint is you have to be aggressive when inserting the magazine. It now is my pride and joy.

  • Colombian Comet

    Just picked up my Ruger SR 556 “American Iron” for only $1,429, I am going to shoot it in a few days, can’t wait. Looking to get a Trijicon Reflex sight, which model can be recommended?
    Loving Life,

  • Roger Mann

    Getting the SR 556 would be a great weapon to have. Being out in a deployed environment, weapon endurance and the weapons ability to fire even in harsh weather conditions is key to me. A more accurate weapon makes me have to work less in different shooting positions. I think it would be a joy to fire this weapon.

  • Blaine

    This is a pretty Cool rifle but I lik to sick o my yougoslavin Ak 74 better.

  • Ryan

    Ruger has had my rifle for 2 months. SR556 is junk. Buy a S&W and put the money you save into mods.

  • Charles

    Wooooooooo Whooooooooo! I picked one up last week for $ 1,585 and 20 boxes of Winchester 55 gr FMJ priced at 10 for eighty-five dollars along with three more Magpul magazines for forty-five bucks. All gone – ate ’em up flawlessly. There is definately no post purchase dissidence with this kid here. This piece is one of the best show and tell thingies I’ve ever owned. Altough the MSRP might seem high to many it really is a relitive bargain if you consider all it’s features.

  • Vik

    All serious operators know there is no free lunch.
    Gas piston assemblys have to be kept cleaned, they add weight and vibration.

    I’ll stay with my familiar and highly reliable
    Hartford Old mare.

  • jon

    What laser is used in the picture? Thanks!

  • Wil

    What scope rings where used for the picture? Thanks Wil

  • Mike Stanton

    Old man Ruger must be turning in his grave, with this gun. What the hell does Mark Gurney know about this weapon, he couldn’t even make easy castings for me in his hayday at PineTree

  • doug lafarge

    Hi, I’m looking at the new ruger ar-15 model on the cover of october’s magazine and I really like the green laser that’s mounted on the rail, could you tell me what kind it is? Thank you, Doug

  • tom

    great gun owner of many ARs this one is my favorite,and is also my most reliable AR yet even better than my bushmaster or RRA.the price is high but you get what you pay RRA has better accuracy as it should with a much longer barrel.