Faxon ARAK-21® 16" 7.62×39 Caliber Conversion Kit

The Faxon ARAK-21® 16" 7.62×39 Caliber Conversion Kit is the factory-engineered way to convert your ARAK-21® upper to 7.62×39—built around the same long-stroke piston architecture that makes the ARAK platform run clean and reliably across variable ammo types. This kit is designed as a matched system: a dedicated 7.62×39 Barrel Assembly Unit (BAU) and a caliber-specific bolt engineered for the cartridge’s larger case head, increased bolt thrust, and common hard-primer ammunition.

7.62×39 isn’t a “just swap the barrel” cartridge—so we didn’t treat it like one. The 7.62×39 ARAK-21® bolt uses a larger firing pin for improved ignition reliability, plus extractor geometry sized for the larger rim radius. The gas ports on the 7.62×39 regulator are tuned specifically for the cartridge’s pressure curve, and the ARAK’s adjustable regulator gives you the ability to tune function to your ammo and conditions (run the lowest setting that locks back reliably for reduced wear and recoil).

Made in-house by Faxon Firearms in Greater Cincinnati, Ohio, this conversion kit is purpose-built for shooters who want the ballistic performance and widespread availability of 7.62×39 in a modern, piston-driven, folding-stock-capable platform—without giving up the precision manufacturing and systems-level engineering that define the ARAK-21®.

Key Features

• Factory 7.62×39 conversion for the Faxon ARAK-21® platform
• 16" 7.62×39 Barrel Assembly Unit (BAU) for fast caliber changes
• Dedicated 7.62×39 bolt (not interchangeable with 5.56 bolts)
• Larger firing pin to aid ignition with common hard-primer 7.62×39 loads
• Extractor geometry sized/shaped for 7.62×39 case rim
• Adjustable gas regulator with 7.62×39-tuned gas porting
• Manufactured in-house by Faxon Firearms (USA)

Use Cases

• Training & range volume: tuneable piston operation for mixed ammo types
• Field rifles: 7.62×39 energy with modern controls and optics-ready rail
• Folding-stock setups: ARAK system keeps the recoil system in the upper (no buffer tube requirement on the lower)

Installation Overview (From ARAK-21® Manual)

Always verify the firearm is unloaded/cleared before installation.

BAU Removal / Install

1. Remove the ARAK-21® upper from the lower receiver and field strip.
2. Place the upper upside down on a work surface (recommended for easiest BAU removal).
3. Loosen the six screws holding the lower handguard in place (screws are captive).
4. Pull the handguard straight up to remove.
5. Press the existing BAU forward 1–2 inches, then lift the BAU to remove.
6. Install the 7.62×39 BAU: align the trunnion tabs on both sides and press rearward into place.
7. Reinstall the lower handguard, aligning the four steel alignment pins with the recesses.
8. Tighten the six handguard screws to 30 in-lbs.

Gas Regulator Tuning (Quick Start)

• Confirm the gas adjuster is correct for the barrel/caliber (7.62×39 uses caliber-specific tuning).
• Start on a reduced gas setting and test lock-back with a single round.
• Increase gas setting only as needed until the bolt locks back reliably.
• Important: Do not fire with the regulator in the insertion/removal (disassembly) position.

7.62×39 Reliability Notes

• Many 7.62×39 loads use harder, military-type primers. Faxon recommends a full power hammer spring, full mass hammer, and removing the firing pin buffer spring to ensure reliable ignition with “Russian spec” ammunition.
• The 7.62×39 BAU and bolt are designed to work together and are not cross-compatible with 5.56 BAUs/bolts. Always verify correct caliber components and ammunition.

Internal Links

• ARAK-21®
• ARAK-21® Caliber Conversion Kits

Warranty

All Faxon Firearms products are backed by our Limited Lifetime Warranty.
For full warranty terms, service instructions, and exclusions, please visit:
https://faxonfirearms.com/warranty-privacy-terms/