Knight’s Armament URX 4 forend: Initial thoughts

I ordered a 13″ AR-15/M16 URX 4 forend (100-015-202) from Brownells for an upcoming project.

The URX 4 is Knight’s latest rail system offering, utilizing a one piece design with an Integral Barrel Nut (IBN). The top of the anodized aluminum URX 4 features a STANAG rail, while the other sides accept KeyMod modular accessories. The URX 4 includes two steel QD inserts located at 3 and 9 o’clock on the rear of the forend.

Installation is simple. The barrel is seated in the upper and the rail tightened into place. A series of provided shims (similar to those provided with various muzzle devices) is used to index the rail at top dead center. Knight’s supplies a proprietary wrench to torque the rail into place.

13" URX 4 forearm installed — 13″ URX 4 forearm installed

Steel QD inserts are located on each side of the URX 4.

The URX gives the user plenty of mounting options for KeyMod accessories.

The gas block screws are accessible through the KeyMod slots in the rail.

I like the handling characteristics of the URX 4. I normally only run a light (9 o’clock) and IR-laser (12 o’clock) on my carbines. The remaining rail surfaces on typical four rail forend systems add weight without seeing use. The Knight’s URX 4 is lighter and slicker. For instance, my Daniel Defense 12.5″ RIS 2 weighs in at 19.4 ounces versus the 13″ URX 4 at 12.7 ounces!