Colt M4 Carbine Federal Patrol 5.56mm NATO 16in Matte Black Semi Automatic Modern Sporting Rilfe - 30+1 - The Colt Federal Patrol Carbine is an advanced rifle based on Colt's legendary M4 platform adding key accessories as requested by the FBI. It features a new Geissele MK4 M-LOK capable free-floated forend, and a set of Magpul PRO flip-up sights.