SOLGW M4-L89 Upper Receiver Group, 14.5-Inch 5.56, Pinned & Welded (HUX)

The SOLGW M4-L89 Upper Receiver Group, 14.5-inch 5.56, Pinned & Welded, HUX configuration (Sons of Liberty Gun Works part no. U-M4L89-556-145-HUX) is a complete upper receiver assembly built by Sons of Liberty Gun Works around a forged upper receiver and the company’s L89 seven-sided rail system. It pairs that rail with a Liberty Fighting Barrel chambered in 5.56 NATO at 14.5 inches, permanently pinned and welded to reach legal rifle-length overall dimensions without an NFA-regulated short barrel. Sons of Liberty Gun Works builds a reputation on tight quality control across its small parts and barrels, and this upper carries that same standard through to a complete, ready-to-run assembly. It’s a strong option for builders who want SOLGW’s fighting-rifle pedigree without machining or assembling the upper themselves.

Key Specifications

• Chambered in .223 Rem/5.56 NATO for broad ammunition compatibility.
• Features a 14.5-inch barrel, permanently pinned and welded to reach legal rifle length.
• Built around a forged upper receiver for strength and durability.
• Uses the L89 seven-sided rail system for a wide, versatile accessory-mounting platform.
• Fitted with a Liberty Fighting Barrel, Sons of Liberty Gun Works’ proprietary barrel line.
• Sold as a complete Upper Receiver Group, ready to pin onto a compatible mil-spec lower.
• Offered across multiple length and muzzle device options in the M4-L89 upper lineup.
• Pairs the L89 rail with a forged upper for a rigid, duty-ready accessory-mounting platform.
• Configured in the HUX variant, one of several muzzle device and finish options SOLGW offers on this upper.

Frequently Asked Questions

Is this upper legal to own without an NFA stamp? Yes, the 14.5-inch barrel is permanently pinned and welded to reach legal rifle-length overall dimensions.

What rail system does this upper use? Sons of Liberty Gun Works’ L89 seven-sided rail.

Buy the SOLGW M4-L89 Upper Receiver Group

Add SOLGW’s fighting-rifle pedigree to your build without machining an upper yourself. Order this Sons of Liberty Gun Works upper from our AR15 uppers selection for fast, insured shipping from our Lubbock, Texas gun shop.