Faxon Firearms Arak-21 Urssb762 Arak 21 16 7.62 Cmp Upper

The Faxon Firearms ARAK-21 16" 7.62x39 complete upper receiver is a gas piston–driven, tool-free upgrade for your existing AR-15 lower. Unlike standard AR uppers, the ARAK-21 uses a long-stroke variable gas piston system and installs in under a minute with just the two existing takedown and pivot pins—no gunsmithing, no special tools, no modifications to your lower receiver needed. This is purpose-built for shooters who want the reliability and shootability of a piston gun without replacing their entire rifle.

The 16" medium barrel arrives pre-assembled in a complete Barrel Assembly Unit (BAU) with gas block, adjustable gas piston, and a 3-port MuzzLok muzzle brake already attached. The gas adjuster knob offers three user-selectable flow settings for tuning to different ammo loads, plus a fourth position that locks off gas flow entirely for single-shot operation—handy for suppressed shooting or training scenarios. The machined billet upper features a full-length top Picatinny rail (laser-engraved for optic placement) plus three additional rails at the muzzle end in M4 quad-rail configuration, giving you plenty of real estate for lights, lasers, and sights.

Internals are where the ARAK-21 diverges from standard AR tooling. The 8-lug bolt design, hardened steel carrier rails, and self-contained firing pin retention system deliver noticeably smoother cycling and better longevity than conventional setups. The ambidextrous, non-reciprocating charging handle folds and relocates left-to-right without tools. Fair warning: most AR-15 parts won't swap in here—only the firing pin, extractor spring, and ejector spring are cross-compatible. This upper is its own ecosystem, but that design philosophy is exactly what gives it the piston gun advantage in a package your current lower can immediately accept.

Shipping includes the upper receiver, one BAU (16" barrel pre-assembled), muzzle brake, charging handle, three aluminum Picatinny rail sections, three insulating shims, bolt carrier assembly, recoil springs and guide rod, owner's manual, and BAU removal tools plus Allen wrenches for rail attachment. If you're running 7.62x39 and want piston reliability without an upper receiver overhaul, the ARAK-21 is a straight swap.

Key Features

• Gas piston system with three user-adjustable gas flow settings plus single-shot lockoff
• Tool-free installation—mounts to standard AR-15 lower in under one minute using existing pins only
• Full-length picatinny rail on top (laser-engraved) plus quad-rail muzzle section for optics and accessories
• 8-lug bolt with involute profile; hardened steel carrier rail system for smooth, durable cycling
• Ambidextrous, non-reciprocating charging handle; folds and relocates without tools
• Complete Barrel Assembly Unit pre-assembled with 16" medium barrel, gas block, and 3-port muzzle brake
• Self-contained firing pin retention; compatible lower allows folding stock installation

Specifications

Frequently Asked Questions

Does the ARAK-21 upper work with my standard AR-15 lower receiver?

Yes. The ARAK-21 interfaces with any standard AR-15 lower using only the existing takedown pin and pivot pin. Installation takes under one minute with no tools and requires zero modifications to your lower.

What parts are interchangeable with a standard AR-15 upper?

Only three: the firing pin, extractor spring, and ejector spring. The ARAK-21's unique design means most other AR components won't swap in. This is by design—the piston system and carrier rail architecture are fundamentally different from standard AR-15 uppers.

What's included in the package?

The upper receiver assembly, one 16" Barrel Assembly Unit (barrel, gas block, gas piston, and 3-port muzzle brake pre-installed), charging handle, bolt carrier assembly, three aluminum Picatinny rail sections, three insulating shims, recoil springs with guide rod, owner's manual, BAU removal tools, and Allen wrenches for rail attachment.

Can I use a suppressor or run single-shot?

The gas adjuster knob includes a lockoff position (fourth setting) that blocks gas flow entirely, allowing single-shot operation—useful for suppressed shooting or training. The three other settings tune gas flow for different ammunition loads.