ARAK-21 Upper Receiver - CUSTOM

ARAK-21 Upper Receiver - CUSTOM

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Lead Times Are Currently 8-12 weeks
Size Chart

ARAK-21® Features

Components of the ARAK-21® Upper Receiver:

The ARAK-21® is a gas piston actuated, complete upper receiver assembly designed to seamlessly interface with the standard AR-15 platform.  The total extent of the interface is simply the take down pin, and the pivot pin.  The new ARAK-21® upper receiver offers you all its features with no change to your current lower receiver and can be installed in less than one minute with no tools. 

Your ARAK-21® upper receiver will be shipped to you with one “Barrel Assembly Unit” (BAU), or two, depending on which package you purchase.

The BAU is comprised of the barrel, gas block, muzzle brake, gas piston, gas adjuster, and barrel trunnion.  The only removable part of this assembly is the gas adjuster knob.  The gas adjuster knob has 4 settings.  Three of the settings allow different gas flows for optimum operation, and one setting blocks the gas flow for a single shot operation.

The upper receiver includes the charging block, standard charging handle, lower forearm with screws, three aluminum full length picatinny rails, three insulating shims, bolt carrier assembly, lower recoil lug with spring guide rod, and dual recoil spring system.  Along with your new ARAK-21® upper receiver you will receive your owners manual, and two allen wrenches that will fit the screws that attach the lower forearm, and the front picatinny rails.

Due to the unique and innovative features of the ARAK-21® upper receiver, there are very few parts that are interchangeable with a standard AR-15.  The firing pin, extractor spring, and ejector spring are the only parts that are standard and interchangeable with an AR-15 upper receiver.

Other features include:

  • The upper receiver is fully machined from an aircraft grade 6061-T6 aluminum billet in a one piece design that incorporates a full length picatinny rail (Mil-STD-1913) on the top and three additional rails on the muzzle end of the receiver, making it a full M4 style quad rail upper.  The top picatinny rail is laser engraved for optic placement.  There are also half-length picatinny rails available.
  • 12 ½” length BAU is available in 5.56, heavy profile. 16” and 20” length BAU’s are available in both the 5.56 and 300 BLK. There are two profiles to choose from, medium and heavy.  BAU’s can be interchanged in less than 3 minutes by removing the (6) captive allen screws on the bottom rail using the enclosed allen wrench.  
  • Long stroke variable setting gas piston system.  There are three options for gas flow, and one for no gas flow.  This allows for single shot operation.  There is also a clean out port for the gas block between the gas cylinder, and the barrel.
  • Charging handle is ambidextrous, non-reciprocating, foldable, spring returned and is easily relocated from left to right side without tools by the operator.

  • Model “39” Eight (8) lug bolt design with involute profile for both right and left hand versions.  The extractor is positioned at 3 o’clock.  This allows for a left hand version to use the same bolt by simply removing the cam pin and rotating 180 degrees and reinstalling the cam pin.
  • Self-contained firing pin retention system enclosed in a rectangular bolt carrier that no longer requires a cotter pin.
  • Bolted in hardened steel rail system for the bolt carrier to ride on.  This allows a metal on metal wear surface for better wear characteristics and a much smoother operation.
  • The ARAK-21® system allows for a folding stock to be added, as our recoil system does not extend beyond the upper receiver to fully operate.  This eliminates the noise and feel of the buffer tube cycling back and forth.

PLEASE NOTE:Images shown may include items not sold with the ARAK-21® Upper Receiver.


ARAK-21 Upper Receiver Includes:

  • ARAK-21 Upper (As Ordered)
  • Shipping Box
  • Manual
  • BAU Removal Tools
  • Magazine Marker Bands (300 BLK & 7.62x39, if ordered)
  • Bolt(s) & Firing Pin(s) for Ordered Calibers
  • Recoil Spring(s) for Ordered Calibers

Faxon Technical Note on 7.62x39 Caliber Kit:

  • The factory recommends a high-power hammer spring to use with the 7.62x39 kit. 
  • Many aftermarket "light" triggers will not reliably ignite 7.62x39 surplus ammunition.  
  • A spring is included and installed on XRS rifles ordered with the caliber. It is sold separately for the upper or caliber kit only. 
  • Faxon offers a Wolff high power spring for sale. 
  • Faxon recommends HiperFire triggers with a special spring kit for an improved trigger pull. Contact HiperFire for details.


  • The complete rifle weighs in less than 7 lbs, with no magazine or accessories. 
  • The standard ARAK-21 upper receiver with a 16" medium barrel weights in at 5.5 lbs. Pencil barrels remove .3 lbs and heavy barrels increase the weight .3 lbs. 
  • Uppers equipped with 12.5" medium barrels weigh approximately 5 lbs. 
  • Heavy 20" barrels increase the base weight approximately .5 lbs. 

300 BLK Compatibility:

Due the fixed gas system length of the ARAK platform and variability of 300 BLK subsonic ammunition, a suppressor is required for reliable function with the 300 BLK BAUs using subsonic ammunition and supersonic on the 12.5" barrel. 


Note to California Residents:

Due to changes in California gun laws we are no longer able to sell/ship the ARAK-21 XRS to California.

Returns Policy
You may return most new, unopened items within 30 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.

We can ship to virtually any address in the world. Note that there are restrictions on some products, and some products cannot be shipped to international destinations.

When you place an order, we will estimate shipping and delivery dates for you based on the availability of your items and the shipping options you choose. Depending on the shipping provider you choose, shipping date estimates may appear on the shipping quotes page.

Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can be found on its detail page. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.

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21 Reviews Hide Reviews Show Reviews

  • ARAK-21

    Posted by Donavyn Estep on Apr 25th 2018

    Great product, fit and finish are great, very happy with the performance of mine.

  • ARAK-21 Upper Receiver Custom

    Posted by Brent Bruce on Sep 14th 2017

    Absolutely love my ARAK. I get lots of curiosity looks at the range, all due to the lack of visible recoil when firing. What looks like an AR sends onlookers reeling when they realize there is little to no recoil. Accuracy is spot on with 1.85 groups at 100 yds. No dirty back end after firing either. LOVE IT!

  • Best side charging upper!

    Posted by Kellen Fraser on Jul 14th 2017

    Love the arak 21 system, runs flawlessly. Very unique looking upper. The barrel is super accurate, sub moa!

  • Faxon made one great upper receiver. I finally got my gun built and got to take it out to test it. It worked great!! I was very impressed and the quality of the upper is just superior. Had a little issue feeding some ammo but thanks to the gas settin

    Posted by Ryan on May 17th 2017

    Great work Faxon!

  • ARAK-21 Upper Receiver

    Posted by Gustavo on Apr 11th 2017

    This is truly one of the best hybrid designs I have come across. it has taken me over a year to consider my options and Faxon has delivered to my every expectation with their ARAK-21 product. The tolerance on this upper is so tight, it fits like a glove on my Spike's Tactical lower receiver. Beyond pleased with the product and the Faxon team. The wait may be long, but so worth it if you are looking for a great hybrid system that supports multiple calibers. Thanks Faxon, I will be purchasing more of your products in the near future.


    Posted by James on Oct 14th 2016

    I am a US Army SOF veteran. I have used multiple weapon systems during my career. I have beed waiting for an rifle that had the best of both worlds. Finally FAXON came out with the ARAK 21! I would recommend using "Troy Industries Micro HK Style Front and Rear Folding Battle Sight". I zeroed my ARAK at 25 yards and then zeroed my red dot sight. No problem hitting targets at 300 meters! I am giving ARAK 21 5 stars!!

  • Best ak and ar hybrid

    Posted by Tango Bravo on Oct 13th 2016

    I love ar's but respect the durability of a ak47! This is the best of both worlds as advertised. I had a long wait to get this upper but it was well worth it. I know the DoD wants to adopt a new platform this would fit the bill! Faxon maybe you can do what colt and other gun manufacturers did with the m4 and farm out production? I'm very impressed with the fit and function of the arak21.

  • precision at it's finest.

    Posted by rob on Oct 13th 2016

    Tolerances are tight. Recoil is smooth and flat. The ergonomics are excellent. But one now before Hillary puts a stop to it.

  • ARAK21 6 month owned

    Posted by Archer C on Oct 8th 2016

    After seeing this firearm in photos for years I bit the bullet and saved for it. I purchased the upper and another barrel. Putting it on my NFA compliant lower because the barrel is 12.5" taking it out to shoot was an experience. The weapon fires smooth. Really smooth! This is my first piston driven firearm and the difference is amazing. Faxon has done a great job with their precision machining. Everything's tight and moves smoothly. With their muzzle brake the weapon is loud! All in all it's a piece of art. Only con is its kinda front heavy but I went with a heavy barrel too. Still 5 stars in my book

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