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

Key Specifications

• The chambering is 5.56 NATO, the standard AR-15 cartridge.
• Barrel length is 14.5 inches, a carbine length built around SOLGW’s Liberty Fighting Barrel.
• The barrel is the Liberty Fighting Barrel, SOLGW’s own design.
• The receiver is a forged upper, matching mil-spec AR-15 fit.
• The handguard is the L89 seven-sided rail, SOLGW’s own handguard design.
• The muzzle carries an ASR interface, for suppressor-mount compatibility.
• It is sold as an upper receiver group only, with no lower included.
• It mates to a standard mil-spec AR-15 lower receiver, so any compatible lower completes the build.
• It is intended for competition, duty and personal-defense builds.

Frequently Asked Questions

Does this include a lower receiver? No. It is an upper receiver group only, so you 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? It can. Putting it on a shouldered rifle lower makes a short-barreled rifle; since October 9, 2026, ATF no longer requires Form 1 approval or registration for that, but state law still applies, and taking an SBR across state lines needs an approved ATF Form 5320.20. Built on a pistol lower it is a legal pistol build.

What muzzle device does it use? It carries SOLGW’s ASR muzzle interface, which is designed for suppressor-mount compatibility.

Buy the Sons of Liberty Gun Works M4-L89 Upper Receiver Group, 14.5-Inch, 5.56 NATO, ASR

A complete upper group turns a stripped lower into a working rifle in one order, and the L89 rail is what sets this one apart. Order it from our Lubbock, Texas gun shop for fast direct shipping, and see more AR15 uppers.