The Sons of Liberty Gun Works M4-L89 is a 5.56mm semi-automatic AR-pattern rifle with a 13.7-inch QPQ button-rifled barrel pinned to a 16-inch overall barrel length using a NOX muzzle hider. It has a 30+1 capacity, midlength gas system, black hardcoat anodized receiver, Liberty trigger, and B5 grip. The 13.7-inch barrel is pinned and welded to reach the 16-inch overall length, keeping it in standard rifle configuration without additional federal paperwork. 
 

Key Specifications 

• Brand: Sons of Liberty Gun Works 
• Model: M4-L89 
• Caliber: 5.56mm 
• Action: Semi Auto 
• Capacity: 30+1 
• Barrel Length: 13.7 in (pinned to 16 in OAL) 
• Color/Finish: Black 
   

Detailed Features 

• 13.7-inch QPQ button-rifled barrel pinned with NOX muzzle hider to 16-inch OAL 
• Midlength gas system 
• Black hardcoat anodized receiver with ambidextrous controls 
• Liberty trigger 
• B5 grip

Sons of Liberty Gun Works M4-L89 owners regularly point to the QPQ finish and tight tolerances as evidence of a quality build. The midlength gas system on a 13.7-inch barrel reduces the gas impulse compared to a carbine-length setup, and owners who run the rifle hard report consistent cycling with a range of ammunition.

The Liberty trigger is a frequent highlight in M4-L89 feedback, with most owners describing a clean break that holds up without immediate aftermarket replacement. The B5 grip and ambidextrous controls are well-received, particularly among left-handed shooters who find the setup genuinely usable. The 13.7/pin-and-weld configuration appeals to those who want the handling of a shorter barrel without additional federal paperwork.

Sons of Liberty Gun Works prices at a premium over basic AR builders, and the value debate is predictable. Supporters cite the fit and finish along with the QPQ barrel treatment; critics argue the components are not meaningfully different from a quality mid-tier build. Most owners who have put rounds through the M4-L89 report satisfaction with the result.