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Brand: Faxon Firearms
Availability:  Lead Times Are Currently ~8 Weeks

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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.

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



  • 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



  • 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 seperately for the upper or caliber kit only. 
  • The factory offers a Wolff high power spring for sale. 
  • The factory 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. 



The 300 AAC BlackOut barrels are designed to function reliably with supersonic ammunition stand-alone and subsonic ammunition when used with suppressor. The 12.5" barrel may not be functional with all ammunition. It will be important for the end-user to establish the best performing ammunition. 

Note:  The use of a suppressor will improve the function and reliability of the 12.5" 300 AAC Blackout ARAK-21® barrel.

Additional Information

Additional Information

Brand Faxon Firearms

Sales@GunCalifornia.com | 800-221-6816 | 3277 S. White Rd #315, San Jose, CA 95148

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