STORY AND PHOTOGRAPHS BY OLEG VOLK
The AR57 (also known as the AR Five Seven) upper receiver for the AR-15 has two claims to fame: a 50-shot capacity and downward ejection for ambidextrous operation. Operating by simple blowback, this upper is available in 6-inch pistol and 16-inch riﬂe versions, with the latter being reviewed here.
Manufactured by the eponymous AR57 LLC, and chambered in 5.7x28mm, this upper is less powerful than the standard 5.56mm version, but it has certain tangible advantages, including reduced muzzle blast, a high practical rate of ﬁre, nonexistent recoil, and the ability to use folding stocks. Since the buffer is located within the receiver, folding stocks may also be used for compact storage or carry.
To load, place the baseplate of a standard FN P90 magazine into the recess on the front of the upper, then press the feed lip side down on the catch located above and slightly back of the bolt. To charge, pull on the right-side nonreciprocating handle and release. The right-side charging hand placement makes it accessible for operation by the strong hand. Since it only has to be operated once every 50 shots, the time penalty for moving the hand off the pistol grip isn’t too great.
Empties will eject downward through the nominal magazine well. Some people use a 20-round magazine body with the feed lips, spring and follower removed to act as a brass catcher.
The magazine has no provision for activating the bolt lock when empty, but the bolt can be locked open using the catch on the lower. The upper runs very cleanly and reliably, requiring no maintenance after the ﬁrst 500 shots.
The AR57 comes with a medium ﬂuted barrel, reasonable for a varmint riﬂe but excessive for a defensive carbine. Burning around six grains per shot, 5.7x28mm runs much cooler than 5.56mm, which burns four or more times as much. That yields much reduced muzzle blast and far greater heat endurance, of course at the cost of a roughly 40 percent slower bullet.
The adequacy of 5.7x28mm for stopping human aggressors has been in dispute ever since its introduction. Some of the lighter bullets available for the caliber have traditionally been tipped or leadless hollow points prone to excessive fragmentation. Firing a 27-grain lead-free hollow point at a full, upright 12-ounce beverage can did not produce a complete penetration – an excellent result for a range or a small varmint round, but not a man-stopper.
Expanding ammunition with better penetration is also available from FN, along with nonfragmenting 40-grain FMJ American Eagle. Recently, RR Weapon Systems introduced two 37-grain all-copper loads, 37F (fragmenting) and 37X (expanding). In testing 37X, I found it much hotter than the alternatives and a very reliable terminal performer. The three-petal bullets expanded to ﬁll 2/3-inch circumference and penetrated around 12 inches into gel. Velocity was around 2,680 feet per second with a standard deviation of under 10, so it was no surprise that it produced groups a touch under 2 inches. Other than handloads with 40-grain Vmax, all other ammunition grouped closer to 2.5 to 3 minutes of angle when ﬁred using a 2.5x scope.
The main limitation on the use of an AR57 for varmint control is the space available for optics. Because the magazine is lifted up for unloading, the potential length of the scope is sharply limited. I have been able to ﬁt 2.5x or 4x prismatic scopes, but anything longer caused interference. Considering these sighting limitations, I would rate it as suitable for small rodents out to 100 yards.
Accuracy is a less important consideration for defensive use. Follow-up shots with the AR57 are limited only by the trigger ﬁnger dexterity, as it showed no muzzle rise at all. Up close, this platform would be better served with a red dot sight and a laser for rapid aiming. I’d like to see a defensive variant with a pencil-thin barrel and a more skeletonized forend developed alongside the current version.
Compared to the PS90, the AR57 is the heavier option, even when polymer lowers are used. It is also longer. But the advantages of an AR57 are numerous. Even a stock AR-15 has a better trigger than a PS90, and aftermarket options can enhance that difference a great deal. AR lowers allow adjustable length of pull, and AR ergonomics make more use of existing training, other than in the reloading process. The height of sights over bore is signiﬁcantly less, making accurate hits easier.
Compared to a 5.56 upper, the AR57 is simpler to clean, generates less felt recoil and much less muzzle blast. With no protruding magazine, it allows the shooter to get very low into a prone position. Two full 50-round P90 magazines weigh as little as one 5.56 30-rounder, so you can carry a lot of ammunition.
At $745 direct from the manufacturer or an authorized dealer, it is less expensive than a PS90 carbine (which lists at $1350), even after the cost of an AR-15 lower is added in. The 5.7x28mm ammunition costs about the same as 5.56x45mm, though the variety of available loads is deﬁnitely smaller.
The niche I see for AR57 – besides it being plain fun to shoot – is for self-defense by the same slightly built individuals who would have picked an M1 carbine in the past. It requires less upper body strength to use than most long guns, and gives 50 shots without reloading. A small teenager or a fragile senior can run it with ease, but the rest of us won’t need an excuse to enjoy using this upper. ASJ
Editor’s note: For more information about the AR57, visit 57center.com.
THE SEVEN-SHOT MAGAZINE is genius. The thick stainless-steel lips are smooth to the touch, and all seven rounds can be loaded quickly and effortlessly. Since all of the external edges are smoothly radiused, a handful of these mags can be carried in a pocket with no worry of them scratching each other.
You won’t ﬁnd a magazine catch on this gun. The magazine is retained on both sides by a springy mag well. The magazine locks in solidly until the shooter pulls down on the magazine with moderate effort, and they cost around $22 each. Even though I have several, I found myself just reloading the same one in the ﬁeld because the process was so quick and effortless.
The seven-shot capacity is dictated by the curve of the ammunition stack. If there were more than seven, the cartridge would have to curve forward even more, requiring a more complex magazine body shape.
ALL VARIANTS OF the Model 722 come with a crisp 2-pound trigger with an overtravel adjustment. The bolt has a locking lug opposite the handle, which acts as a second lug. The action is smooth and easy to run. The symmetrical design operates with only a 50-degree throw, easily clearing even the largest scopes. The short 1.5-inch cycle distance makes for very quick loading. The short length of the action permits a 20-inch barrel on a very light and compact gun. The 13.25-inch length of pull makes it feel even smaller. The safety is a lever – forward for ﬁre, back for safe. It clicks very positively, but the angle of throw is fairly small, so it’s sometimes hard to tell at a glance if it’s on. On the left side of the receiver there is a spring-loaded bolt retainer. The bolt does have to be cycled briskly for reliable ejection.
KEYSTONE ARMS’ SISTER company is Revolution Stocks, a premier aftermarket manufacturer. It’s no surprise that the stock quality for all three variants is superb, with a tight wood-to-metal ﬁnish. The decades of metalworking experience behind the Crickett brand also make for excellent action ﬁt. Keystone didn’t skimp on the manufacturing process – even the trigger guard is a nicely machined part.
THE CLASSIC IS lightweight at just 4.6 pounds, and feels even lighter, thanks to the good balance. The Varmint is a couple of pounds more, but the sculpted thumbhole stock makes
steadying it off-hand quite easy. The Classic comes standard with Williams Firesights, ﬁber optic front post and semibuckhorn rear that adjusts for windage and elevation. Picking up the front is very easy in any kind of light, but the bright ﬁber optic pipe on the front sight obscured at least 2.75 inches of the bull’s-eye, making precise alignment difficult. At best, my groups were 2 inches at 25 yards. After trying several kinds of ammunition, I gave up and scoped it with the dedicated Primary Arms 6x rimﬁre BDC scope in low rings and tried again. The results improved greatly: From prone at 80 yards, the CCI Green Tag ammo grouped at 1.25 inches, or about 1.5 minute of angle. Ammunition quality matters. Bulk .22 gave me 3MOA at best. Even with bulk Federal ammo, the BDC reticle made hits on pop cans placed 50 yards downrange routine. Shooting off of a lead sled indoors, without wind, produced 1.25MOA with Aguila Match, 1MOA with Aguila Super Extra subsonic and 2MOA with Federal 550-round bulk pack. I am guessing Green Tag would have come in at about 1.25MOA as well.
THE REAL ACCURACY testing was with the Varmint version. Prone at 25 yards produced a single seven-shot hole scarcely larger than the bullet diameter. Topped with the superb 6-24x Weaver with an adjustable objective, this riﬂe made extreme accuracy the default result. The slim 1-inch tube with a 40mm objective permitted low rings and thus minimal sight height over bore. The mildot reticle provided for drop compensation, and the focusable objective made for a crystal-clear view of the bull’s-eye obliterated by precision ﬁre. Both CCI Green Tag and Aguila Riﬂe Match grouped near 0.6MOA, and Eley Match was right at 0.5MOA at 50 yards – a great performance for any riﬂe, and even more so for the budget-priced 722.
One exception to the versatility of the Varmint model comes from its match chamber incompatibility with the CCI Stinger hypervelocity round often used by actual varmint shooters. The Aguila equivalent works ﬁne, as does the Winchester, but neither hypervelocity load equals the standard velocity loads in outright accuracy under controlled range conditions. In the real world with wind drift and imperfect range estimation, the faster loads perform almost as well as the match bullets.
Twin forend studs allow for simultaneous installation of a bipod and a shooting sling. Despite the greater weight, I consider the Varmint version the best of the three models not only for rested shooting but also for ﬁeld hunting. The exception would be left-handed shooters, who would have to stick with the ambidextrous Classic stock design.
OTHER THAN THE QUICK but imprecise iron sights, Classic is a strong competitor to CZ455 Military Trainer. With optics, the 722 Varmint gives up nothing at all to the competition. Overall, the riﬂe is just fun to use. Its operation is so transparent that it feels like a natural extension of the marksman. ASJ
Editor’s note: For more info, go to keystonesportingarmsllc.com.