Ruger SR-556

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, and 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; this severely limits the options of the end user, and it’s nothing that 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 good that 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 that 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. A decent soft case, three Magpul PMags, the aforementioned Troy rail, Ruger marked Troy front and rear folding iron sights, three rail covers, and a Hogue grip are the items that immediately come to mind.

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” will have 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 55gr 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, but 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.

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 – but 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, but 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 will hang up on one another, causing the weapon to become completely nonfunctional. This is fine as a safety feature to make lawyers happy, but 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 that were 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.



Filed under Firearms

3 responses to “Ruger SR-556

  1. Sooooo… it’s heavy, has proprietary parts and lawyer fire control parts, an unstaked castle nut, and a canted receiver extension tube; remind me again why you wanted this? 🙂

  2. Kristofer_G

    I give Ruger credit for trying. I believe with the SR556 they have just missed the mark on have a suitable defensive or duty carbine. The addition of a Government or Light-Weight contour 1/7″ barrel and a M16 profile BCG would do much to move the SR556 into that market.

    After that, it will simply take time, and a few brave souls, for long term reliability and durability reports to come out.

    However, I do not know if the general public is ready for a rifle with an adjustable gas system…

  3. Zef M.

    I am still waiting to find someone that is going to do a head to head test with the piston gun system. I know most gun writers would be skittish to pit a gun against another and report one failed. I did find this entirely interesting as just the simple things that we expect from gun builders be there that this one lacked. Thanks for the report!

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s