Ruger 5902 Sr556 M4 Review Assignment

Traditionally, Ruger has not been known as a “tactical” gun maker. Part of that is due to Bill Ruger and his background. Growing up in New England before WWII, he basically came to business with the old-money blueblood attitude, and took that attitude into politics. (Or, at least as much politics as a gunmaker gets dragged into.)

He designed machine guns during WWII, and after the war he designed and built products for the sporting market that were breathtaking in their utility, and used production methods that didn’t just “bend the cost curve” but hammered it flat. The Ruger Standard, later the Mk 1, a .22 LR pistol that sold for half of what the comparable Colt product did, was just the start.

Focused on making better and more-affordable hunting rifles and handguns, he really wasn’t plugged into the defensive market. And, to be fair to the late Bill Ruger, the defensive market as we now know it really didn’t exist for the first couple of decades he was designing and making firearms.

As a result, when it came time to confront the growing plague of gun control efforts, he simply (from my view, anyway) fell back on the educated upper-class N’Easterner attitudes he’d grown up with. To whit: men of good intentions can get along, and learn to compromise, and everyone will be happy and benefit. Too bad he was in a back-alley knife fight with uncompromising opponents.

After the infamous “I don’t know why a law-abiding citizen needs a magazine bigger than that” episode, Ruger was off the buyer’s list for a lot of shooters. I know of shooters who for a long time would not allow a Ruger firearm into their home. Not only would they not buy them, they wouldn’t have any of them where they exercised control: their castle. And when they did move into the new-to-them market segment, Ruger didn’t move into the defensive arena with much authority, certainly not with the authority it had brought to the struggle with Colt, Remington and S&W.

That has changed recently. With the introduction of the SR9, a striker-fired hi-cap 9mm pistol meant for defensive carry, and its follow-up the SR9c, plus the LCR and LCP, Ruger clearly was taking the defensive-arm struggle to its competitors. Even with a thorough game plan and preparation, Ruger was unprepared for the reaction to a proper entry into the defensive firearms market. They announced the LCP (Light Carry Pistol), a compact .380, at the SHOT show. A four-day national industry convention, it is where many manufacturers unveil new products.

By the end of the show, Ruger had orders for some 50,000 pistols. A month later, they had orders for over 100,000. When they announced the SR9 a year later, the demand was so great that Ruger stopped production of all other products at the Prescott, Arizona, plant except for the LCP and the SR9.

Those two pistols alone were requiring more production capacity than the entire plant, devoted to the entire rest of the Ruger pistol line beforehand, could provide. Ruger spent quite some time even getting close to catching up. So, it was with great interest that a bunch of us gun writers recently gathered at a private range for a writers-only retreat. There, we had manufacturers showing us the guns, gear and ammo that they’d be unveiling for the public months or nearly a year after our little soiree.

Everyone was waiting to see what new bombshell Ruger would unveil. A new snubbie revolver? A pistol in .40 S&W? When the SR556 came out into view, the crowd was stunned nearly speechless. (And when you consider the crowd, that’s quite a feat.) Not at the sheer technical prowess of the product, but rather at the amazing fact that this was a Ruger-made AR-15. Not something someone else made, re-branded, but a Ruger rifle, from the large to the small parts.

And a Ruger design in the heart of it, too, for it is a piston-driven gun. At the range session later that day, we took turns doing the obligatory “piston gun demo” where we each shot a magazine or two quickly, removed the bolt, and held it in our hands to show how cool it was. When it was my turn in front of the camera, I quipped, “We now know that the end of the world is near. This is a Ruger.”

And it is quite the blaster, too. When it comes to entering the AR market, Ruger did not do as others had done, and enter at the basic-gun end of the market. As a manufacturing and marketing decision, that was a good one. The AR buying craze was in full swing when Ruger brought theirs to market, but anyone with any business sense knows that balloons don’t last forever. When the bubble bursts, the low-margin basic (fill in the blank) segment of the market takes more than a beating; it becomes a bloodbath.
So Ruger pulled out all the stops when it came to the SR556.

First of all, no, it is not the HK416 in US-made guise. Not that I have any feelings, good or bad, towards the HK 416. While I’m admiring of the engineering that went into it, I also think they (in typical HK/German fashion) over-engineered the thing. Had Ruger copied the design, and if HK had any patents on it, then by all means, HK would sue Ruger and I’d be in favor of it. If HK hadn’t patented any of it, and Ruger copied it, well, too bad/so sad. As much as I’m a proponent of the defense of intellectual property rights, if you don’t patent it, too bad.

Were we to declare otherwise, the late Soviet Union, via their agent Mikhail Kalashnikov, would have owed the estates of John Moses Browning and John Garand money for every AK-47 and -74 they’d made. (And since Garand was a government employee, any of his designs belonged to the US, and thus the Soviet Union would have been paying us.) Short answer: it isn’t any kind of patent infringement.

The Ruger design is a short-stroke non-venting system that uses an internal piston in the gas block and a spring-loaded transfer rod to drive the carrier. It is their own design.

The movement of the piston is the control (and the adjustable throttle, more on that in a bit) and is what regulates the transfer rod movement. Only so much gas can go through the gas port and drive the piston, and excess pressure simply drives the piston harder, but not all of that excess is delivered to the transfer rod. But, we’re getting a bit ahead of ourselves, so let’s start from the beginning.

Once you get past all the “whose design did they use?” nonsense, you get to enjoy the wonder that is a Ruger offering in this day and age. The box itself is a cardboard carton with “SR-556” and the Ruger logo printed on it. I suspect in 50 years (assuming we still have guns, or a civilization) that the cardboard box itself will be a hot item in the collector’s market, since most users will simply toss it.

Inside that is a relatively discreet rifle carrying case in black synthetic cloth, with the Ruger logo and name bonded to it, in red. The rifle itself comes with three Magpul PMag30 magazines, black windowless, a set of rail covers, an owners manual, and the Federally-mandated lock. (I sometimes wonder which of our legislators had a family business in the lock industry.) There’s no cleaning kit and no sling, which is fine by me. I have a box full of factory-supplied cleaning kits and slings (and padlocks) that I never have a need for, so leaving them out doesn’t hurt me in any way. But if you were expecting a cleaning kit or sling and don’t currently have one of either, you’ll have to buy one of those on your own.

The rifle itself? Oh, boy. The lower is a small-pin (there had been some early rumors that Ruger had used the same large-diameter hammer and trigger pins that Colt used for a couple of decades. Wishful internet rumor-mongering, I’m glad to tell you) mil-spec lower marked “safe” and “fire” that, were it not marked with the Ruger lower, would not be distinguishable from any of the host of other mil-spec built semi-auto lowers. It has a Hogue rubber pistol grip with the Ruger logo in it and a six-position telestock with the Ruger logo moulded into it. The safety is not ambidextrous, and the trigger pull is a thoroughly acceptable mil-spec trigger pull.

That is, it is creepy, gritty, and a bit on the heavy side as it comes out of the box. And, just like all the other milspec triggers I’ve ever used, I expect it to improve a great deal with a little bit of dry-firing and use. Ruger has had a reputation for some time of providing “lawyer-proof” triggers on their products. Maybe yes, maybe no, but in this instance we can lay the trigger at the feet of the government. That is, mil-spec.

As plain, ordinary and unremarkable as the lower is, the upper is where all the action is.

First, the upper receiver is a flat-top, machined from a forging, complete with forward assist and ejector lump. The railed, free-float handguards are made by Troy Industries, and they’re marked with the Ruger name and logo. There is another interesting detail to them: they are secured to the upper. There are a pair of roll pins in the upper, one on either side of the joint between the receiver and the handguards at the top, and a single, much bigger one on the bottom.

Clearly, they pin the two together, a good idea with a piston system running in between. The handguards are surmounted by a set of Troy sights, both folding, front and rear. While made by Troy, they are marked with the Ruger name and logo. While Ruger has outsourced primo parts on the items they themselves do not make, they want to make it absolutely clear just whose rifle this is. (And it isn’t your Father’s Buick, for those who remember the old ad campaign.)

The gas block is pinned to the barrel, and the gas regulator is adjustable. It has four settings, from “0” to “3,” and is meant to be self-regulating. Zero means no gas, so if you want to use your SR556 as a straight-pull bolt action rifle, go for it. The other three are increasing amounts of gas. The “1” setting is not meant as a suppressor setting, per se; it just delivers less gas. And the “3” setting is just more gas. Ruger recommends that you not use a setting any higher than needed to run reliably with the ammo you’ve selected. (Factory-new, no reloads, thankyouverymuch.) Those lucky enough to have suppressors will probably run the Ruger on the “1” setting when they have the can installed.

Ruger recommends that ejection be directly out to the side, that is, ninety degrees to the direction you are firing. If it is “late” (Ruger’s term, not mine, nor a common description for ejection) and throws the empties to the rear, increase gas port size/number and keep shooting. If it is “early” (again, Ruger’s term) with brass going forward, turn the gas port/number to a smaller setting. My bet is that since Ruger ships it with the regulator set at “2” and most ammo will work just fine that way, that we’ll see lots of SR-556 rifles with the regulator frozen at “2” after hundreds or thousands of rounds fired.

Most shooters will fire a few rounds, see that the brass is exiting the area with sufficient alacrity and enthusiasm, and ignore the regulator afterwards. And, most shooters being most shooters, they won’t go and wrestle the gas system apart after the first shooting and cleaning session. In a few years, I’d expect gunsmiths to start seeing Ruger SR-556 rifles with carbon-welded gas plugs in place, looking to have them removed for cleaning.

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The two-piece piston, with the front part self-limiting as to the amount of travel it can experience, acts as a thrust regulator, in addition to the gas regulation setting you crank the front knob to.

The transfer rod connects to the thrust shoulder on the carrier. The carrier is machined with anti-tilt pads in the back, with an integral thrust shoulder, and the whole assembly – bolt, carrier, extractor, etc. – is chrome-plated. Right smack dab in the middle of the carrier, where you can see it when the dust cover is open, the carrier is marked with the Ruger logo.

The barrel is a marvel, for those who have been somewhat accustomed to the barrels of the Mini14s of old. Unlike those, which were widely varying in accuracy (some shot OK; a few shot well; and most were only casually accurate), the SR556’s is hammer-forged out of 41V45 steel and has a Ruger AC556-style flash hider on the end. It is also chrome-lined, with a 5.56 chamber and a twist of 1:9. The last part is the only part that the cognoscenti have been able to muster a grumble about.

They’d prefer a rifle with a twist of 1:7, just like the military barrels have. Well, get used to it. A 1:9 will fully stabilize all the common ammo, everything from 68 grains on down. It won’t over-spin the varmint loads. It may even, depending on the individual rifle, stabilize the 75- and 77-grain loads. Ruger has clearly made a decision here that they expect the number of shooters using lightweight, fragile varmint bullets to outnumber (probably greatly outnumber) those who would otherwise be feeding the SR556 a diet of Mk262 Mod 1.

Ruger, in a not-at-all-surprising decision, also makes a model of the SR556 that is “neutered.” That is, instead of the flash hider and telestock, they make one (the SR-556SC) with the stock pinned open and the flash hider gone. It ships with ten-round magazines. So, if you live someplace where the politicians get an attack of the vapors at the thought of an “eeevil black rifle,” you can conform with relevant (albeit idiotic) state law.

Ruger lists the SR-556FB as tipping the scales at 7.94 pounds. My postal scale tells me this one comes in at 7 pounds, 13.3 ounces. That translates to 7.83 pounds, which surprised me. I had been hefting it on the walk to the scale, and was convinced it wasn’t the least bit less than 8.25. The apparent heft comes from the medium-to-heavy barrel profile, which brings the upper all by itself to 5 pounds, 11.7 ounces. That same barrel will valiantly resist heat and change of impact, due to its mass.

At the industry function, we enjoyed ourselves immensely, shooting up every round of ammo to be had. Partly it was the free ammo at the height of the ammo shortage, but it was due in no small part to the experience of shooting a Ruger-marked AR-15.

I waited a while once I had returned from the shoot, but Ruger finally sent me an SR556 of my own to test. On looking it over, I noticed a few interesting details. The serial number, for one, is done in two sets. The “SN” and the 590 prefix are done as one set of stampings, and the actual serial number of the rifle is a separate operation, done in a different font. The markings, the Ruger logo and “SR-556” are done as a different operation also. I wonder just how many stamping machines this poor lower has been through?

The castle nut and back plate of the lower have not been mil-spec staked at the notches, a small but telling detail. And the buffer weight is a standard, not an “H” weight.

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I will never forget how sad I was to surrender the heavy—but accurate and hard-hitting—M14 in favor of a strange-looking toy rifle we called an M16 (technically an M16A1 in my day). We Marines griped about it for decades later as, I’m sure, our predecessors griped about yielding the ’03 Springfield for the newfangled Garand, and then the Garand for the M14.

Eventually, few of us who had actually used the M14 remained. By then we had the M16A2, a very good battle rifle with very good ammunition. But looking back to when I made that painful transition more than 35 years ago, it would never have occurred to me that what we now loosely call the “AR frame” would become one of the most popular military and civilian rifle actions.

Nor, to be perfectly honest, would it ever have occurred to me that a traditional rifle manufacturer like Ruger would introduce a sporting rifle on the “AR frame.” But as Jim Bequette and I drove across Kansas toward Major Bob Stutler’s “Gun Room” in Medicine Lodge that is exactly what I expected to see. Recently retired from Ruger, Stutler and his wife, Dorothy, have been busy remodeling the old Grand Hotel, where we would join some of the Ruger folks for a first viewing of the SR-556, a brand-new Ruger rifle that looks suspiciously like, well, like an AR.

Looks Are Deceiving
Yes, the SR-556 looks, feels, and operates like the old friend the “AR frame” has become. Except it isn’t, not exactly. Custom conversions have been out there for some time, but the SR-556 is the first production “AR-type” rifle designed from the ground up with a piston action, not the familiar gas operation. The big difference is the “Two Stage Piston Drive,” wherein the gas energy drives a piston, which in turn cycles the bolt.

Is this significant? Well, according to Ruger engineers, the piston “reduces initial energy transfer, providing a smoother power delivery stroke.” Since that’s engineer-speak, I can neither confirm nor deny. I can say that I have never fired an AR that was so smooth, or so consistent. Believe it or not, felt recoil is also reduced. With a 5.56 (.223 Remington)? Does that matter? Perhaps not, but I well recall one Qualification Day when I was a captain commanding a rifle company. It was very windy and difficult, and I was snuggling tight and close to my M16 in the standing position. A bit too close: The charging handle smashed my upper lip and chipped a front tooth. I had the high score that day, but also a dentist to visit.

The difference is slight, but if you’re used to the standard gas-operated AR, you will feel it. If you can’t feel it, you will see another difference. Per Ruger: “The Piston Drive system minimizes combustion residue in the action, proving a cooler, cleaner, and more reliably running rifle.” “Cooler” I can’t address. “Cleaner” you’ll see. We had just two SR-556 rifles to play with, and we had lots of ammo. We shot it all, several hundred rounds. I have considerable experience with ARs under lots of conditions. I have never seen such little residue and grime. After a hundred rounds or more the chrome-plated bolt and carrier could be wiped spotless with a dry handkerchief (yes, Marine officers do clean their own rifles, so I know a bit about that as well).

The gas system has variable gas port sizes, the regulator offering four settings (three gas ports, plus “off”). This allows you to tune the gas system to the load. The first two gas settings are generally for “normal operation.” The “off” setting is primarily for manual operation. The highest gas setting, giving the most velocity to the piston, is intended for worst-condition use, perhaps with questionable ammo, when the rifle is dirty, or when the chips are down and the rifle simply must function.

By the way, function it does. As I said, we went through several hundred rounds with nary a stoppage of any kind. We had good ammo, both Federal and Hornady which, of course, helps a lot, but there were simply no problems whatsoever. In all that shooting we never actually cleaned either rifle, although we did wipe down the bolts a couple of times. It would perhaps be inappropriate to describe the piston action as “better”—but for darn sure it works, and I could both see and feel the difference.

Bells and Whistles
Aside from the action, the basics of the SR-556 are an extremely well-appointed “AR-type” rifle incorporating many, if not most, of the features and accessories you might see on a full-out custom AR. Moving parts are chrome-plated; the exterior is manganese phosphate “Parkerized.” The 16 1/8-inch barrel is hammer-forged, chrome-lined, of 41V45 stainless with a 1:9 twist. Slightly nontraditional, but very Ruger, is the AC556 flash hider, same as on the Mini-14.

The lower receiver is pure AR with a single-stage (and quite crisp) trigger, with six-position folding M4 stock. Buffer and spring are mil-spec, with length of pull adjustable from 10¼ to 13½ inches. Note that Ruger didn’t reinvent the wheel with the external features. The stock is a Hogue Monogrip; the handguard is from Troy Industries (its Quad Rail 1913). Those who desire can hang whatever accessories desired on the rails, up to an including a grenade launcher. Those who just want to shoot the rifle and save their tender pinkies can cover the rails with supplied Troy rail covers. And the rifle, incidentally, comes with a soft case that has three magazine pouches.

The upper receiver also has a full-length Picatinny rail. Supplied are fold-up Troy battle sights, with protected front and dual-aperture rear. One of the rifles we shot was “out of the box” with these sights; the second had the battle sights replaced with a Nikon Tactical scope. Complete with three Magpul 30-round magazines, the SR-556 is intended to come out of the box ready for…whatever.

A Joy to Shoot
That “whatever” depends entirely upon who you are, what you do, and what uses you have for a rifle of this type—but one universal truth is that all ARs are just plain fun to shoot. As I said, we ran both Rugers hard and we couldn’t make them jam. Perfect functioning aside, a couple of things struck me as we ran magazine after magazine through the rifles. First was stock fit. The fold-up Troy battle sights are fairly high, about the same height as the center of field of a normal-sized riflescope mounted as low as possible. Height of comb on the stock, at least for me, is exactly perfect for these iron sights, with the rifle coming up smoothly and perfectly on target.

Second, and please forgive me because this primarily a left-handed observation (not the same as a left-handed compliment.): Ejection is fantastic. You see, when a lefty shoots a right-handed AR there is some possibility of brass hitting one’s shoulder and bouncing down into the collar. It ain’t funny, ’cause that stuff is hot when it comes out of the action. Second-degree burns are instantaneous, and we lefties quickly learned to button the top shirt button when shooting our M16s. The SR-556 throws its brass straight out into the stratosphere, no burns and no buttoned collar.

Accuracy with the 55-grain loads on hand was pretty good. Groups with the Nikon scope averaged about 1¼  inches. And indications were that the rifle wanted to shoot better. Most groups were basically tighter, but with five-shot strings often showing an uncalled “flier,” with occasional vertical stringing. This was probably mostly our fault. Our intent was to shoot the rifles and see if they worked (they did), and we were shooting “un-broken-in” new barrels without cleaning them. Okay, I’ll admit it: We had fun running several magazines through the rifles before we got down to shooting groups. In that context, accuracy was pretty darned good. But that’s no surprise. We learned a long time ago that this type of action, mated with a good barrel, shoots very straight.

Fast or slow, bench or offhand, scope or battle sights, the SR-556 was a joy to shoot. It functioned perfectly, and did everything it was supposed to do. It’s basically an AR, and these things are true of all “AR-frame” rifles. With the gas piston, it’s an AR with a difference, and it’s also a factory rifle incorporating a wide range of popular features. Such a rifle is a huge departure for Sturm, Ruger, and Company, clearly reflecting the popularity and huge demand for this type of firearm. They’ve done such a great job with it that I hardly yearned for my old M14.

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