Ruger Small Frame Autoloading Rifle (SFAR): A .308 Win. in a .223 Package

When I began my outdoor writing career back around 2006, it seemed like every rifle I tested was some flavor of AR. Most of them were great guns, but I found myself struggling to say something new and unique about rifles that were anything but. Innovations were subtle and incremental—at best. This year, I finally get the chance to talk about an AR-style rifle that is new and unique. Ruger’s new Small Frame Autoloading Rifle (SFAR) does what no other rifle that I’m aware of has ever done: It is chambered in .308 Winchester but in what is essentially a .223-size package. Let’s take a step back to the 1950s where this story begins. When Armalite’s Eugene Stoner invented the rifle that we know now as the AR, he did so in 7.62x51. This rifle, widely known as the AR-10, was later scaled-down by Stoner and Jim Sullivan into what would become the 5.56x45 AR-15.

Though the features were similar, AR-10s are significantly larger and heavier—two pounds, on average—than AR-15s, making them less desirable for widespread use. Over the years, many users have sought the punch of the AR-10 but without the weight and bulk, leading ballisticians to effectively max-out the power available on the smaller format rifle. The result was the development of niche cartridges such as the 6.5 Grendel and 6mm ARC. With the SFAR, Ruger engineers went in a completely different direction. They figured out a way to effectively wedge an AR-10-size cartridge—.308 Win.—into an AR-15-size rifle. The result combines the power, versatility and ammunition availability of the .308 in a light and handy package.

From the outside, the SFAR basically looks like an AR-15 with an AR-10-size magazine well. The SFAR is currently available in two formats: the Model 5611, a full-size rifle with a 20-inch barrel, and the Model 5610, a 16.10-inch barreled carbine. They weigh in at 6.8 and 7.3 pounds respectively. I tested the more compact Model 5610. Both rifles wear cold-hammer-forged 4140 chrome-moly barrels made in-house by Ruger. Rifling is 5R, and twist rate is the standard 1:10. Barrels are black nitrided for corrosion and wear resistance, so combined with the durable results of the hammer-forging process and the nature of the .308 Win. cartridge, the life of a barrel should be extremely long.

The barrels are threaded 5/8x24 and equipped with a Boomer muzzle brake, which has two ports per side. Since the muzzle is threaded, a variety of muzzle devices can be installed, including suppressors. I did not mount a suppressor to the SFAR during testing, but doing so would have been as simple as removing the brake. True to Stoner’s original design, the SFAR is direct-impingement gas-operated. The 5611 uses a rifle-length gas system while the 5610 I evaluated uses a mid-length setup. To accommodate the wide variety of loads on the market and to maximize reliability, a four-position rotating gas regulator is located at the forward edge of the gas block, under the fore-end. The gas regulator constricts or expands the diameter of the gas port, allowing the user to control the flow of gases into the receiver. The system is adjusted using a 3/16-inch hex wrench that comes stored inside the hollow pistol grip. Notches on the side of the regulator allow for improvised methods of adjustment in the field if the wrench is misplaced. A screwdriver will work, as will something like a pocketknife if you’re really desperate. There is a reason that most 3-Gun competitors use adjustable gas systems: They can be a really effective means of keeping the muzzle on-target. The first regulator position allows for maximum passage through the gas system, maximizing reliability.

At the second position, less gas is allowed through, which cuts recoil and what I call “bolt carrier bounce”—the effect of the carrier slamming the buffer rearward with more force than is necessary to cycle the action. The third position is even more restrictive and is designed for use when a suppressor is attached to the barrel since these devices can create significant back pressure from trapped propellant gases. The final position is a shutoff, effectively making the rifle a straight-pull bolt action. Ruger recommends running the gas regulator at the lowest setting at which the rifle will function reliably with the chosen ammunition. The simple method of determining this setting is to dial down the regulator until reliability suffers, then open the system back up one step. When in doubt or when reliability trumps all else, run the system wide-open. The magic to the SFAR, though, it is under the hood. How did the engineers make this work? They started by increasing the strength characteristics of the bolt and the barrel extension that it interfaces with.

There are steels today that simply weren’t available when the AR was designed. Taking advantage of these materials, the SFAR’s bolt and barrel extension are machined from a high nickel content, high-strength steel that can handle the increased load of the .308 Win. Although the bolt carrier group is of similar size to the AR-15s, the two are not interchangeable. The lugs on the SFAR’s bolt are beefed-up and tapered, adding additional strength. The bolt carrier, the profile of which is noticeably different, is machined from 8620 steel and is chrome lined. The firing pin, made from titanium, is DLC-coated.

The SFAR ships with a 20-round Magpul PMag detachable box magazine, but it is designed to be compatible with all AR-10/SR-25 mags on the market. The .308 case is obviously larger and heavier than that of the .223, so a more robust ejection system was necessary. The SFAR uses two plunger-type ejectors that extend from the breech face. A traditional, though larger, AR-style extractor is used. I tested the gun at the most-forgiving gas regulator setting, but reliability was 100 percent with all three loads used. One of the stars of this show is the trigger. The Ruger Elite 452 two-stage trigger broke repeatedly at 3.3 pounds, which is far better than the advertised pull weight. Zero creep was detected. The safety/selector is a standard AR-type, as is the charging handle and the forward assist. Anyone comfortable with a modern sporting rifle will be able to manipulate the SFAR’s controls without issue.

The SFAR 5610 is built with a free-floating, 15-inch, Lite aluminum handguard. There is a short, railed section toward the muzzle and another section back toward the receiver while the three, six and nine o’clock fore-end positions are M-Lok compatible for accessory mounting. QD sling inlets are integral and are situated on both sides of the handguard. The SFAR is equipped from the factory with a Magpul MOE SL stock that allows the user to adjust the length of pull to six positions, ranging from 11 to 14.25 inches. Since the buffer tube is the standard mil-spec size, any AR-15-compatible stock that uses that tube diameter can be installed. The pistol grip, also a Magpul MOE, is AR-compatible also and simple to change out if desired.

Before shooting the SFAR, I assumed it would be a handful in terms of recoil. I was wrong. Despite being significantly lighter than a traditional .308 semiauto, recoil was mild—even with the gas system in its wide-open position. I credit the muzzle brake for this lack of felt recoil. Given the potential versatility of the SFAR, I wanted to test it with an appropriately capable optic. I’ve become a big fan of the stable of variable-power scopes that are capable of true 1X magnification. These scopes are as fast as a red dot at close range but can be used for precision shooting at longer distances. I had an EOTech Vudu 1-10x28mm on hand, and it was a perfect match for this carbine. I test-fired the SFAR with three factory loads and found it to be an accurate setup, with some impressive groups along the way. The best three-shot group overall came from the Federal Premium Gold Medal Berger load. It measured just 0.41 inch.

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So the SFAR is no doubt innovative, but what is it good for? Well, I live in the heart of feral hog country, where these destructive creatures wreak havoc on agriculture. Trapping is a more effective management tool, but hunting them is more fun. Night hunts are common. AR-10s are a very popular tool among those who are serious about going after them, but honestly, I’ve never wanted to lug that much weight around. When you start with a nine-pound rifle and then add a thermal or night vision optic as well as a suppressor, you’re carrying a heavy and bulky load. To me, the 16.1-inch-barreled SFAR is the solution to this problem, and it just might be the perfect hog gun for such endeavors.

The .308 chambering of the Ruger SFAR begs the question of whether other similarly sized chamberings are on the horizon. A 6.5 Creedmoor seems possible, especially given that it shares the same maximum pressure specification of the .308. A 6mm Creedmoor? A .243 Win.? Ruger is tight-lipped regarding future models, but that doesn’t prevent us from speculating. I expect the SFAR line to grow significantly. Given the amount of innovation that has taken place in the AR world over the past two decades, I shouldn’t have been surprised by or skeptical of the SFAR, but I was. Just when we assume that we’ve seen it all, a company surprises us. Ruger’s use of modern materials and innovative engineering methods has produced an incredibly capable but portable rifle and carbine. A reliable and accurate semiautomatic .308 weighing less than seven pounds is truly something special.

Ruger SFAR Specifications

• Type: direct-impingement AR
• Caliber: .308 Win.
• Capacity: 20+1 Magpul PMag detachable box magazine
• Barrel: 16.1 in. (as tested); 1:10 twist, threaded 5/8x24
• Overall Length: 34–37.25 in.
• Weight: 6 lb., 13 oz.
• Finish: Type III hardcoat anodized, black nitride
• Stock: Adjustable Magpul MOE SL
• Sights: None; Picatinny rail sections on fore-end and receiver
• Safeties: Two-position receiver-mounted lever trigger two-stage, 3.3 lb. pull (measured)
• Price: $1,229
• Manufacturer: Ruger, ruger.com