KAK Industry Complete AR-9 Upper — 4" / 9mm

Upgrade your next AR-9 build with this complete upper assembly from KAK Industry. Chambered in 9mm, it features a durable 4" button-rifled barrel and a sleek 5.5" M-LOK free-float handguard, offering excellent modularity and balance for pistol-caliber carbine and pistol builds. This upper ships fully assembled and includes a bolt carrier group, charging handle, forward assist, and dust cover — ready to install.

Key Features

• Barrel Length: 4"
• Barrel Material: Button-rifled 41V50
• Chamber: 9mm NATO
• Twist Rate: 1:10"
• Muzzle Device: KAK Flashcan (1/2-36)
• Gas System: Blowback
• Upper Receiver: Forged 7075-T6 aluminum, precision machined to M16/M4 spec
• Handguard: 5.5" M-LOK free-float, 6061-T6 with proprietary clamping system and heavy-duty barrel nut
• Charging Handle: MIL-SPEC with enhanced large billet latch
• BCG: One-piece auto-profile carrier, 8620 steel, black nitride finish
• Compatibility: Works with Colt and Glock style magazines
• Includes: Bolt carrier group and charging handle

Details — Upper

Barrel: 4" button-rifled 41V50 barrel chambered in 9mm NATO with a 1:10" twist. Designed for reliable blowback operation and paired with the KAK Flashcan muzzle device (1/2-36). The 5.5" M-LOK free-float handguard is machined from 6061-T6 and uses a proprietary clamping system with a heavy-duty barrel nut for a secure fit and repeatable zero.

Details — Bolt Carrier Group (BCG)

BCG: One-piece auto-profile carrier machined from aircraft/bearing-quality 8620 steel, properly heat treated and finished with black nitride. Firing pin machined from 8740, precision ground, and chrome plated. One-piece billet fully machined enhanced extractor, phosphate coated for improved reliability and corrosion resistance. S7 tool steel ejector and extractor retaining pin. 4130 gas key, nitride, precision staked using a hydraulic staking machine. Carrier key screws are Grade 8, heat treated and staked.

The weighted one-piece BCG is tuned to work with a wide range of hammer types and is compatible with Colt and Glock style magazines.

Charging Handle: MIL-SPEC charging handle with an enhanced large billet latch for positive manipulation.

Testing & Notes

All KAK complete upper receivers are test-fired by KAK Industry for feed and function using commercially loaded ammunition — no guesswork, no hassle.

Please note: KAK Industry 9mm uppers do not support last round bolt hold open (LRBHO) functionality when used with KAK AR9 lowers.

By purchasing this product, you confirm compliance with all federal, state, and local laws regarding firearm ownership.