![urx 4](https://i0.wp.com/rifleshooter.com/wp-content/uploads/2014/07/urx-4.jpg?resize=400%2C381&ssl=1)
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](https://i0.wp.com/rifleshooter.com/wp-content/uploads/2014/07/URX-4-upper-side-view-3.jpg?resize=300%2C200&ssl=1)
![Steel QD inserts are located on each side of the URX 4.](https://i0.wp.com/rifleshooter.com/wp-content/uploads/2014/07/URX-4-qd-stud.jpg?resize=300%2C200&ssl=1)
![The URX gives the user plenty of mounting options for KeyMod accessories.](https://i0.wp.com/rifleshooter.com/wp-content/uploads/2014/07/URX-4-key-mod-slots.jpg?resize=215%2C300&ssl=1)
![The gas block screws are accessible through the KeyMod slots in the rail.](https://i0.wp.com/rifleshooter.com/wp-content/uploads/2014/07/URX-4-access-to-gas-block.jpg?resize=227%2C300&ssl=1)
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!
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