ARAK-21 Gas-Piston Upper Receiver for AR-15 Lowers from Faxon Firearms

by Jeff Quinn

photography by Jeff Quinn & Boge Quinn

April 19th, 2014


Click pictures for a larger version.







Gas regulator.





Charging handle.





Recoil spring.



Disassembly is quick and easy.





Switching barrels takes about two minutes.



The ARAK-21 was mounted atop an Anderson lower for review.



The ARAK-21 uses the standard AR lower bolt catch / release.



3Bucc Brass Catcher.



A few weeks ago, I received in here for review an upper receiver for the AR-15 style rifle. For several days, it sat in the box, as I was busy traveling and working on other projects. I would notice the box as I walked past it, and I was thinking, "It's just an AR upper. I will get to it shortly". However, upon finally opening the box, I was met with an unexpected piece of machinery. The ARAK-21 is not just another AR-15 upper.

The ARAK-21 is a long-stroke gas-piston system that seems to borrow design features from both the AK and the AR designs. The piston system is simple, rugged, adjustable, and reliable. The gas regulator (adjuster) has four positions; three for functioning under various conditions, and another setting that shuts the gas off completely, rendering the weapon a manually-operated rifle. The ability to adjust the amount of gas used to operate the weapon allows it to function reliably if dry, dirty, using weak ammunition, or with a sound suppressor.

The ARAK-21 upper attaches easily atop a mil-spec AR-15 lower, using the pivot pin and the rear take-down pin, just as with any AR rifle. The ARAK-21 does not use the buffer tube spring to return the bolt carrier into battery. Instead, the ARAK has its own recoil spring contained in the upper receiver. This allows the weapon to use standard AR-15 buttsocks, no buttstock, or a hinged folding buttstock, offering a lot of versatility in weapon configuration.

The upper receiver of the ARAK-21 is machined from 6061-T6 billet aluminum and incorporates a full-length 1913 Picatinny rail. The unit shown here is finished in a matte black, but more colorful versions are offered, if desired. The handguard/forearm also has sections of Picatinny rail positioned at three, six, and nine o'clock, and each of these rail sections are removable, if desired. The handguard/forearm is machined integrally with the receiver for exceptional strength and rigidity. The ambidextrous charging handle is located alongside the forward portion of the upper receiver, is spring loaded, and does not reciprocate with the bolt carrier. The handle can be easily switched from the left to the right side, if desired. The ARAK-21 upper can also be purchased in a left-hand version, and the bolt can be turned 180 degrees for LH ejection.

One interesting and useful feature of the ARAK-21 is that it is very easy to switch from 223/5.56mm to the 300 Blackout chambering just by switching the barrel unit. The barrels are button-rifled, and are offered in both medium and heavy profiles. Switching from one caliber to the other takes about two minutes, and the only tool required is an Allen (hex) wrench. Loosening six captured screws along the bottom of the forearm removes that section of forearm, and the barrel unit slides forward and off the weapon. Installing the extra barrel unit is just as easy, and the 300 Blackout uses the standard 5.56mm magazine, which is cheap and plentiful at this time. The 300 Blackout uses a different recoil spring as well, and switching the spring takes less than one minute, and requires no tools. The 4150 chrome-molly  barrels are offered in lengths of 12.5, 16, and 20 inches. The 5.56mm and 300 Blackout barrels are threaded 1/2x28 and 5/8x24, respectively, for the attachment of suppressors or other muzzle devices. The barrels are supplied with the gas system and a muzzle brake installed. The 223/5.56 barrels are button-rifled with a one-in-seven-inch twist, and the 300 barrels have a one-in-eight-inch twist.

The Faxon ARAK-21 is a very well-made weapon. The machining is flawless. The parts mate together perfectly, and every moving part glides fluidly. The gas system is very simple, composed of large, sturdy parts, and should be as reliable as any piece of machinery can be.

For function and accuracy testing, I attached the ARAK-21 upper to an Anderson Manufacturing lower receiver assembly. The Anderson is a high-quality unit with a very good trigger. Atop the ARAK-21 receiver I mounted a Leupold Mark 4 8.5 to 25 power target/tactical scope, in order to achieve the best possible practical accuracy from the weapon. Functioning was perfect, using both the 223/5.56 barrel unit and the 300 Blackout barrel unit. I did have a problem once with the functioning of the Blackout, but it was due entirely to operator error. I had disassembled the weapon for the video, and did not place the gas regulator in the proper position afterward. Once I corrected that mistake, the weapon again ran flawlessly. My fault.

I fired both the 223/5.56 and the 300 Blackout using a variety of ammunition to evaluate both function and accuracy. The accuracy of the 5.56 was mostly in the two-inch range at 100 yards, but the Blackout fired sub-minute groups with every type of ammunition tested. With Wolf Gold, the 5.56 grouped just over one inch at 100 yards, but the Blackout grouped everything into under one inch, every time.

The Faxon ARAK-21 upper receiver is available direct from Faxon Firearms for $1199 US, as of the date of this review. Extra barrel units are available for $399 US. The ARAK-21 is a solid, reliable, and expertly-crafted upper that offers the versatility and reliability of a long-stroke gas piston gun with the convenience and economy of quickly switching calibers. The ARAK-21 is built right, and built in the USA.

Check out the Faxon ARAK-21 online at

To order quality 223, 5.56mm, and 300 Blackout ammunition, go to,, and

Check out the Leupold Mark 4 and other quality optics online at

Jeff Quinn

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Click pictures for a larger version.











Leupold Mark 4 8.5-to-25 power scope.



Target Shooting, Inc. Model 500 Rifle Rest was used for accuracy testing.



300 Blackout fired sub-minute groups at 100 yards.



300 Blackout fired one-hole groups at 25 yards.



223/5.56mm accuracy was generally in the two-inch range at 100 yards, with Wolf Gold turning in the best performance.