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.
Disassembly of the gas system is simple: push out the piston regulator retaining pin and the parts will simply come out the front. The transfer bar, and its spring, won’t come out. They are part of the gas block, and to remove them you’d have to drive out the pins holding the gas block to the barrel. Such work is not advised. If you really feel the need to clean or lube your transfer rod, I’d suggest a liberal application of cleaner/degreaser via an aerosol can, though the rail openings. Then spray lube afterwards. That detail of disassembly alone is enough to preclude military consideration of the SR556 design. Can you imagine an apopleptic Drill Instructor who cannot have rifles detail stripped?
In firing, the SR556 works just as you’d expect from a Ruger, and recoils just as you’d expect a nearly eight-pound AR to recoil. Lots of ammo downrange, not much push on your shoulder, and empty brass flung to the right, not so far away that you can’t easily find it.
As a premium rifle, the Ruger SR-556 comes with a near-premium price tag. But, once you total up the extras that come on it (railed, free-float handguard, piston system, three Pmags) the rifle becomes a much better-appearing deal. And in fact the gun-buying public can do such simple arithmetic, despite the hand-wringing over the sorry state of our schools.
Ruger has not been able to catch up with demand, not from the moment they announced the SR-556.
This article is an excerpt from the Gun Digest Book of the AR-15, Vol. 3. Click here to get your copy.
Recommended AR-15 Resources:
Find more gun books, DVDs and downloads at gundigeststore.com.