The pilot reported that he was completing a practice instrument approach, and after extending the landing gear he saw 3 green lights, indicating the landing gear were down and locked. He continued the approach as normal and touched down on the main landing gear, but as the nose lowered it continued “straight to the ground.” The airplane skidded on its nose down the runway before coming to a stop. The forward lower portion of the airplane’s fuselage was substantially damaged. Following the accident, the nose landing gear actuator was removed, and bench-tested under the supervision of a Federal Aviation Administration inspector. The test revealed that when hydraulic pressure was removed from extension side of the actuator it began an uncommanded movement in the opposite, landing gear retraction, direction. This uncommanded movement was likely due to internal leakage in the actuator, which would have prevented the nose landing gear from remaining in the fully down and locked position.