The M4 and 416 recce collars are a standardization of the original custom made NSWDG recce collars. The M4 recce collar is designed to fit the original 17/16.5" Lilja M4 barrels and the AE recce barrels. The 416 recce collars are designed to fit 14.5" SOCOM HK and Nefarious Arms 416 barrels.
The collars are secured by a set screw. If you choose to use the Lilja barrel you will need to dimple the barrel for the setscrew. If you use the AE or 416 barrel the collar will seat against a step.
