The Sons of Liberty Gun Works M4-L89 upper receiver group (brand part no. U-M4L89-556-145-ASR) pairs a 14.5-inch, .223 Remington/5.56 NATO Liberty Fighting Barrel with a forged upper built around SOLGW’s L89 7-sided rail handguard, finished with an ASR muzzle device interface for suppressor-mount compatibility. SOLGW builds its small parts and uppers to fit most mil-spec firearms, aiming the M4-L89 line at builders assembling a rifle for competition, duty, or personal defense. This AR15 upper is sold as an upper receiver group only, with no lower included.

Key Specifications

• Chambered in .223 Remington/5.56 NATO.
• Barrel measures 14.5 inches, built as a Liberty Fighting Barrel.
• Forged upper receiver paired with SOLGW’s L89 7-sided rail handguard.
• Finished with an ASR muzzle device interface for suppressor-mount compatibility.
• Suited for competition, duty, or personal-defense builds per SOLGW’s design philosophy.

Frequently Asked Questions

Does this include a lower receiver? No. This is an upper receiver group only; you’ll need your own compatible AR-15 lower to build a complete rifle or pistol.

Does a 14.5-inch upper make my rifle an NFA short-barreled rifle? Only once it is assembled onto an already-shouldered, complete rifle lower without a barrel of at least 16 inches. Mounting this upper on a shouldered rifle lower without a prior ATF Form 1 approval to build an SBR would create an unregistered short-barreled rifle; building it as a pistol on a compatible pistol lower avoids that concern entirely.

What does the ASR interface add? It’s a muzzle device interface built for quick-attach suppressor mounting, separate from the barrel and upper themselves.

Buy the SOLGW M4-L89 Upper Receiver Group, 14.5in, 5.56, ASR

A Liberty Fighting Barrel with a suppressor-ready ASR interface is a proven foundation for a duty or competition build. Order this from a Lubbock, TX gun shop and our team will get your order processed right away.