Faxon Firearms Arak-21 5.56 Nato Rifle Non-Threaded Rifle Barrel 12.5in Custom 1-8 Twist Conversion Kit Black. 62x39 to 5.56 NATO in a matter of minutes with this caliber conversion kit for the ARAK-21. The kit includes a Barrel Assembly Unit (BAU) bolt firing pin and firing pin return spring. By swapping out the barrel and bolt you will be able to swap calibers on your ARAK-21. Built for modularity and durability the ARAK-21 affords the end user to configure the weapon system to fit their needs. Specifications for Faxon Firearms Arak-21 5.56 Nato Rifle Threaded Rifle Barrel: Manufacturer: Faxon Firearms Color: Black Caliber: 9mm Luger Barrel Profile: Medium Barrel Twist Rate: 1-8 Barrel Material: 416R Stainless Steel Flutes: No Gun Make: AR Platform Gun Model: Faxon ARAK-21 Condition: New Package Contents: Faxon Firearms Arak-21 5.56 Nato Rifle Threaded Rifle Barrel What firearm models does the manufacturer say Faxon Firearms Arak-21 5.56 Nato Rifle Threaded Rifle Barrel is compatible with? The manufacturer says that Faxon Firearms Arak-21 5.56 Nato Rifle Threaded Rifle Barrel is compatible with Faxon ARAK-21Faxon Firearms ARAK21BAUCONVKIT-104S-12: Arak-21 5.56 Nato Rifle Non-Threaded Rifle Barrel 12.5in Custom 1-8 Twist Conversion Kit Black