The DHC-7, N273EP, was substantially damaged when the nose landing gear collapsed during landing roll at Bucholz Army Air Field at Kwajalein in the Marshall Islands. No injuries were sustained by the airline transport certificated pilot or second pilot, the flight attendant, or 15 passengers. The flight was operated by Raytheon Systems Engineering for the United States Army and departed Kwajalein at 20:29 destined for Roi-Namur. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed. Approaching Roi-Namur, when the landing gear was lowered, the nose gear indicated unsafe and, without landing, the flight returned to Kwajalein. According to the operator’s accident report, the pilot-in-command viewed the nose gear alignment marks in the nose gear inspection window and believed the nose gear was down and locked, and that the gear unsafe light was an erroneous indication. During the landing rollout, the nose landing gear slowly collapsed as the weight of the aircraft settled on the nose. The operator’s investigation revealed a failure in the boss area on the extend end of the nose gear actuator. The operator also determined that the flight crew did not complete the emergency gear extension procedure as specified in the Airplane Flight Manual. During recovery of the aircraft from the runway the emergency gear extension hand pump lowered and locked the nose gear in 8 strokes of the pump. Probable Cause and Findings The failure of the flight crew to properly execute the emergency landing gear extension procedure in response to a landing gear unsafe cockpit indication.