The FN M16A4 upper receiver group — a factory-original, new-production take-off from the FN 15 Military Collector Series M16, built to the M16A4 program specification with a 20" 1:7 chrome-lined rifle-length barrel and a Knight's Armament M5 RAS rail.
The M16A4 — a 20", flat-top, rifle-length successor to the M16A2 — remained the issued long rifle across several Marine Corps infantry units well into the GWOT era. Its defining hardware is the Knight's Armament M5 RAS rail and the MaTech 600m rear BUIS; both are present on this upper exactly as issued. Because this upper is a take-off from the FN 15 Military Collector Series rifle — a commercial FN build produced to FN's exacting military specification — every component downstream of the receiver carries the same pedigree as FN's military contract work. FN, alongside Colt and LMT, is one of the three primary contract manufacturers of M16-family rifles for U.S. forces.
Specifications:
For builders assembling a clone-correct M16A4, the hard part has always been sourcing the program-spec KAC M5 RAS with the correct MaTech BUIS on a matching FN-marked upper — most of what shows up on the secondary market is mismatched commercial parts in the right silhouette. This upper solves that problem in a single SKU.
We've got these in new, factory-packed condition while FN's Military Collector Series take-offs are available. Copy that — grab one while they're here, and we'll get it out the door fast. This item must ship to an FFL holder. No civilian exceptions.
FN
