Faxon ARAK-21® 12.5" 7.62×39 Caliber Conversion Kit

The Faxon ARAK-21® 12.5" 7.62×39 Caliber Conversion Kit is the factory-engineered way to configure your ARAK-21® upper for a compact 7.62×39 setup—built around the ARAK’s long-stroke piston operating system and a matched 7.62×39 BAU + bolt combination. This isn’t a simple barrel swap. 7.62×39 has a larger case head, increased bolt thrust, and commonly uses hard primers—so the BAU, gas tuning, extractor geometry, and firing pin design are purpose-built specifically for the cartridge.

This kit’s dedicated 7.62×39 bolt is engineered for the cartridge’s characteristics, including a larger firing pin to help with ignition reliability, and an extractor claw sized/shaped for the larger rim radius. The included 7.62×39-tuned gas system works with the ARAK’s adjustable regulator so you can tune function to ammo and conditions—run the lowest setting that locks back reliably to reduce wear and recoil.

Manufactured in-house by Faxon Firearms in Greater Cincinnati, Ohio, the 12.5" 7.62×39 conversion is built for shooters who want compact handling, strong terminal performance, and piston-driven reliability—while keeping the ARAK-21® platform’s optics-ready rail and modern ergonomics.

Key Features

• Factory 7.62×39 conversion for the Faxon ARAK-21® platform
• 12.5" 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

• Compact builds: 12.5" handling with 7.62×39 performance
• Training & range volume: tuneable piston operation for mixed ammo types
• Folding-stock setups: ARAK recoil system is contained 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 you get reliable lock-back with your chosen ammunition.
• 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 and engineered 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/