Ruger SR556

Ruger SR556

Ruger’s Chief Engineer, Todd Wilkinson, had this to say about the Ruger SR-556C:

“Many of our customers appreciate the limited muzzle rise when shooting the original SR-556, which allows them to re-acquire their sight picture more quickly between shots, however, some customers requested a shorter, lighter, faster handling gun that can more quickly acquire separate targets. This new SR-556C drops a full half pound off the front end of the gun, which changes its handling dynamics considerably, something our customers are really going to appreciate.”

Ruger AR-15, the SR-556, is now available chambered in 6.8mm SPC. The SR-556/6.8 has .850 heavy contour barrel with a 1:10 twist. It comes packaged with a 5 round and a 25 round magazine.

I’m going to be honest. I would probably never purchase this rifle. It just has too many drawbacks, in my mind –

  • It’s heavy
  • It has an extreme forward CG
  • It’s not fully end-user serviceable
  • You’re effectively limited to one rail system
  • It’s a gas piston/op-rod weapon.

These are the items that came to mind when I first examined an SR-556 at the 2009 NRA show in Phoenix.

Evidently, Ruger heard enough about weight from customers that they recently introduced the SR556C model, which has a shorter, fluted barrel, resulting in a significant weight savings.

Unfortunately, it also has an integral muzzle device; which severely limits your options and it’s nothing I’d want to deal with. Some may be perfectly happy with it – more power to them. It’s just something that makes me scratch my head and wonder, “What were they thinking?”

It’s a good thing they listened to consumer demand regarding weight though.

You’re probably asking yourself why I bothered with this rifle, given the previous few paragraphs. Well, although I had shot one, I had not owned one, and I figured it would make for an interesting comparison with the POF P-415 I have for T&E.

In addition, a major reason for acquiring it (in a trade, I should add) was to determine the center of gravity of the weapon, and add it to my weight and balance calculators. I’ll get to that later.

First, an overview of the weapon.


The SR-556 includes a number of nice extras, the following of which come immediately to mind:

  • A decent soft case
  • Three Magpul PMags
  • The aforementioned Troy rail
  • Ruger-marked Troy front and rear folding iron sights
  • Three rail covers
  • A Hogue grip

The supplied stock is modeled after the Colt M4 stock body, with minor differences in construction that cause it to weigh approximately 1 ounce more than the M4 stock. I found it wholly inadequate for the purposes of balancing out the muzzle-heavy weapon, so I immediately installed a Vltor EMod.

Any decent “fighting rifle” has a white light, so on went a spare Surefire G2 with drop in LED, and I also added an EOTech XPS 2-0.

With these items, the three rail covers, and a 30-round PMag loaded with 55-grain ammunition, the weapon weighed in at almost 10 pounds 8 ounces. I should add that the XPS is less than 2 ounces heavier than an Aimpoint T-1 Micro in a LaRue mount, so if you want an optic and a light on your SR556, you’re going to be staring at 10 pounds loaded even without a heavier stock.

While swapping out the stocks, I checked the receiver extension tube to see if it was straight. Like every other SR556 I’ve examined, it was not. This is easily avoided during assembly – the tube needs to be held straight while the castle nut is being tightened or the tube will turn with the nut.

This really will have no effect on the function of the weapon, although it provides some insight on assembly and QC practices.

Ruger SR-556s are test fired with a full 30-round magazine. This is a test regimen I wholeheartedly approve of, and wish more manufacturers would follow the same regimen.

This is the wear on the receiver extension tube after test firing. It is similar to the wear my Ares converted AR exhibited after a similar round count. Like the Ares weapon, the receiver endplate has not been staked to prevent nut rotation; so far, unlike the Ares weapon, carrier impacts on the tube have not caused the nut to come loose, allowing the stock to rotate and the weapon to become nonfunctional. There is no excuse for any hard-use AR—especially for a piston/op-rod AR—to not have this item staked.

Ruger is a recognized industry leader in investment casting, and it’s my understanding that they make their own fire control group parts. This can be a mixed blessing, yet the trigger pull is quite good for a stock trigger, with little to no grit. Unlike other manufacturers, Ruger does not put grease on the fire control group contact points.

Ruger utilizes a notched hammer and a non-shrouded firing pin carrier. Should the disconnector fail, these items hang up on one another, causing the weapon to become completely nonfunctional. This is fine as a safety feature to make lawyers happy; it is not preferable for a weapon that one might stake their life on.

Moving to the front of the weapon, we see the Ruger muzzle device, similar to those used on Mini-14 variants. The barrel, as many know, is hammer-forged 41V45, chrome lined, with a 1/9 twist rate. The profile can only be described as very heavy.

The gas port is forward of the standard midlength location, and the massive gas block is pinned with two massive pins pressed in with a massive press. These pins are the reason why the weapon is not completely user-serviceable (although Adco Firearms tells me that they can remove the gas block without any problems, allowing them to reprofile or flute/dimple the barrel – normal disassembly rates apply).

The gas regulator is easily adjustable with the mouth of a cartridge case or other such object, but seems very resistant to unintended rotation. It offers four positions, from “no gas” to “full gas.”

The bolt carrier group has been completely hard chromed, with the exception of minor pins and the ejector. It weighs in at 11.1 ounces, the same as the lightest of AR-15 bolt carrier groups. For the sake of comparison, the POF P-415 bolt carrier group is 11.4 ounces, and a standard M16 carrier group is 11.5 ounces.

Though the extractor spring did not appear to be as large or have as much oomph as the Bravo Company extractor springs offered in their upgrade kits, it did have an o-ring installed.


I have only conducted very limited function testing as of yet (it works so far). I’ll be at the range in the next few days and will update the blog accordingly.

Side note – A friend of mine is a gunsmith for a major firearm retailer, and he tells me that he’s had 5 Ruger SR556s returned for functional issues. When he tested them, only one of the five actually exhibited problems – failures to extract with Wolf. Given the appearance of the extractor spring, I’m not completely surprised. As for the other four, maybe the owners decided that they just didn’t like the weapon. If so, that’s a pretty crappy way to deal with it. Don’t lie to a dealer in order to get a full refund on a used product that works fine.

Today I made it to the range with the SR-556. I had 6 other rifles to shoot, so the total round count was limited, but I started to get a better feel for how the weapon handled.

I was in luck – also at the range was Mike Pannone of CTT Solutions and Viking Tactics. An all-around good guy, Mike seems always willing to take a minute (or an hour) to help me with my shooting technique. Today, he ran me through a drill he was working on for the Border Patrol agents that he’s paid to train – two shots to the chest and one to the head of a silhouette at 20 meters, two shots at an IPSC A zone steel plate at 50 meters, then two to the chest and one to the head of the silhouette again, and finally back to the steel plate for 2 more hits.

My times with the Ruger SR-556 and an EOTech were in the 10.5 second range, though I was consistently missing shots on the steel plate at 50 meters. Shooting his own AR, Mike was in the low 6 second range – he said an 8 second run was, for him, “slow”. Note that the EOTech XPS2-0, my time with it having expired, has been replaced with my well-used 552 on a LaRue LT-110 riser.

Below, I run through the drill with a BCM lightweight midlength. The steel plate is the black dot to the left of the silhouette. With the BCM (equipped with a TA33 ACOG), my times were in the high 8s to high 9s – no misses. Although the magnified optic certainly helped, it took a little time to get used to the extra weight out at the front of the Ruger, and I kept “overshooting” as I switched from target to target, which led to frustration, wailing, and gnashing of teeth on my part.

I did not bother with accuracy testing after zeroing the optic, though the weapon seemed consistent enough for the task at hand. Later, I shot the drill once more with the Ruger. It was a “clean” run – no misses – and although the timer was not available, the pace was similar to my earlier ~10-11 second runs. I should add that Mike Pannone considers a 10.2 second “clean” time to be average for the shooters he was training.

Recoil is quite mild – as one might expect from a 10.5-pound AR-15 with a rubber buttpad shooting .223 American Eagle. Still, recoil characteristics are not ideal, and the weapon exhibited a little more muzzle rise than I expected. As you can see in the first picture of this review, fired cases were ejected between 4 and 5 o’clock—more to the rear than I’m used to. I left the weapon on setting 2 for the day, and experienced no malfunctions. My only functional complaint—if I really wanted to get nit-picky—was that the selector was stiff when going from “fire” to “safe”, but not “safe” to “fire”.

After that last drill, I tried holding the rifle at the ready for as long as I could—after only a few minutes, my arm became quite sore. Unlike a lightweight standard AR, which I feel that I could hold at the ready or low ready for a very long time, the SR556 was just too much for my weak limbs to hold up all day.

My initial impression of this weapon is that it is a decent firearm – it functions, and it puts the bullets where you want them to go. If you are willing to train with this weapon and this weapon alone—or its SR-556C brother—you will probably do quite well with it (them), and be happy with the performance of the weapon(s). However, as an AR-15, for my intended use, it is not exactly satisfactory. Its handling characteristics are so different than a “standard” AR-15 that I would find it disconcerting to go back and forth between the two, or at least, I would personally have a fairly steep learning curve every time I switched. It is also unsuited for comfortable all-day carry, such as when hunting or backpacking.

I would like to thank Mike Pannone for taking a good chunk of time out of his busy day to help me out with my shooting yet again. If you get the chance to take a class taught by him, don’t miss out.

First of all, this is a piston gun—and not just an ordinary piston gun, but a two-stage piston gun. Piston guns generally run cleaner an cooler than gas guns and the SR-556 does, too, but the two-stage process softens the acceleration of the carrier group so firing the SR-556 isn’t as a jarring an experience as firing a standard AR-15-type rifle.

Another unique feature is the user-adjustable, four-position gas regulator so shooters can “tune” their gun to shoot cleaner and more reliably with different ammunition. Whether you’re shooting inexpensive “dirty” ammunition, or the finest clean-burning match ammunition, the regulator lets you adjust the gun for optimum performance. And if you like, you can also turn the regulator off, essentially making the SR-556 into a straight-pull rifle. Many will argue that accuracy can be enhanced with the gun set up as such, but what can’t be argued is that turning off the regulator makes use with a suppressor more effective and cleaner.

In addition to those unique features, the SR-556 is equipped with proven, quality parts such as Troy flip up sights and quad rail, Hogue mono-grip, hammer-forged Ruger barrel, a six-position M4-style buttstock and just about everything that can be chromed for durability is. I know I’m looking forward to hearing Craig’s report on how it shoots.

The Ruger SR-556 has been updated. The new SR-556C model is 1.75″ shorter thanks to an integrally machined flash suppressor (ATF counts integrally machined flash suppressor as part of the barrel. The barrel is technically only about 14.5″ long). The heavy barrel is now fluted. Ruger say these two changes drop 1/2 pound off front of the rifle.

The SR-556C offers the same great features that made the original SR-556 such a success: it includes the two-stage piston driven operating system with a four-position adjustable gas regulator; chrome plated, cold hammer forged barrel; Troy Industries Folding Battlesights, Quad Rail, and rail covers; chrome plated bolt carrier group and operating system, six-position stock, Hogue Monogrip and three 30-round MAGPUL PMAG magazines.

Have a new Ruger SR556? Tell us about it in the comment section.

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