SOLGW M4-L89 URG 14.5 5.56 P/W PLN B

Description

The Sons of Liberty Gun Works M4-L89 upper receiver group is built around the demands of duty use and serious training — shooters who run lasers, visible aiming systems, or suppressors and need hardware that holds zero when gear is added, adjusted, or replaced. The core of that stability is the Drivelock barrel nut, which delivers more consistent and repeatable torque than a standard barrel nut, and an internal dowel pin that locks the handguard’s position independently of barrel nut tension alone. Together they reduce the point-of-impact shift that rail-mounted lasers and VAS systems can introduce over time as components are cycled on and off.

The 14.5-inch Liberty Fighting Barrel runs a mid-length gas system, which adds dwell time compared to a carbine-length system on a barrel of this length — the tradeoff being a slightly softer impulse and reduced bolt carrier velocity at the expense of some of the ultra-compact handling a carbine gas system offers. The barrel is 5R rifled with a chrome-lined bore and a .223 Wylde chamber, which accommodates both .223 Rem and 5.56 NATO while maintaining tighter throat dimensions than a standard 5.56 chamber for improved consistency with match-grade .223 ammunition. The exterior carries a phosphate finish and the barrel extension is DLC-coated for wear resistance at the lockup surface.

The 13.75-inch L89 handguard uses a seven-sided M-LOK profile and mounts flush against the receiver, with integral steel QD cups machined into the barrel nut on both sides — no add-on socket required. The Plan B flash hider ships pinned and welded to the muzzle. The upper arrives test-fired from the factory. Bolt carrier group and charging handle are not included.