Knight’s had their entry for the US Army Forward Rail Accessory Kit (FRAK) program. KAC is one of three finalists along with PPI and Adams Arms. The URX IBN rail essentially becomes the barrel nut and comes with a set of shims that can be reused.

Technically, it can be installed by a unit Armorer but in the Army armorers no longer remove barrel nuts so it has to be done at Depot level. It features a removable lower rail that is removed via a detent that can be depressed with a cartridge tip. Then, you can replace the lower rail with an M203/320/26 equipped either with the GI mounting hardware or KAC’s free float versions.
Additionally, you can mount an MRE rail but that is not currently part of the FRAK program. Hopefully, we’ll see that as an ECP or P3I initiative.
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