SOLGW M4-L89 Assembled Upper Receiver Group 14.5" Liberty Fighting Barrel - Pinned Plan B Compatible Flash Hider

SOLGW M4-L89 Assembled Upper Receiver Group
14.5" Liberty Fighting Barrel - Pinned Plan-B Compatible Flash Hider

Built for serious shooters who demand uncompromising reliability and precision, the Sons of Liberty Gun Works L89 Upper Receiver Group is a battle-ready upgrade engineered to the same exacting standards as SOLGW’s legendary rifles. Featuring a forged upper receiver, Liberty Fighting Barrel, and premium components throughout, this upper is test-fired and mission-ready right out of the box.

At its core is the 14.5″ Liberty Fighting Barrel — a 5R rifled, 41V50 chrome moly masterpiece with a phosphate exterior and chrome-lined bore. Chambered in .223 Wylde for optimal accuracy with both .223 Rem and 5.56 NATO, it’s paired with a DLC-coated barrel extension and deep-dimpled .750″ gas journal for rock-solid gas block installation. The L89 rail system adds 7-sided M-LOK slots, integral QD mounts, and SOLGW’s proprietary Drivelock barrel nut system with anti-rotation tabs and internal dowel pin — ensuring a secure lockup and minimal POI shift for lasers and VAS systems.

Pinned & Welded Plan-B Compatible Flash Hider
Pre-installed for suppressor compatibility and reduced muzzle flash.

Forged Upper Receiver
Built to SOLGW’s exacting standards for strength and longevity.

Liberty Fighting Barrel
14.5″ 5R rifled, chrome-lined, phosphate-treated barrel with .223 Wylde chamber for enhanced accuracy.

DLC-Coated Barrel Extension
Improves wear resistance and smooth cycling.

Drivelock Barrel Nut System
Ensures solid lockup with anti-rotation tabs and internal dowel pin for minimal POI shift.

L89 Rail System
13.75″ free-float handguard with 7-sided M-LOK slots and integral QD mounts at the barrel nut.

4140 Gas Block & Nitrided Gas Tube
Durable, corrosion-resistant components for long-term reliability.

Test-Fired Before Shipping
Ensures functionality and performance out of the box.

Specifications

• Barrel Length: 14.5″
• Rail Length: 13.75″
• Barrel Material: 41V50 Chrome Moly
• Rifling: 5R Button Rifled
• Twist Rate: 1:7
• Chamber: .223 Wylde / 5.56mm NATO
• Barrel Extension: DLC Coated
• Gas System: Mid-Length
• Gas Journal: .750″ with Deep Dimple
• Finish: Chrome Lined Bore, Phosphate Exterior
• Muzzle Threads: 1/2×28
• Rail System: L89 7-Sided M-LOK with Integral QD Mounts
• Flash Hider: Pinned & Welded Plan B Compatible Flash Hider
• Upper Receiver: Forged
• Gas Block: SOLGW 4140 Steel
• Gas Tube: Nitrided

*Note: Charging Handle & Bolt Carrier Group Not Included