On November 17, 1994, at 1100 mountain standard time, a Cessna P210N, N731QH, sustained substantial damage on landing at Alamosa, Colorado. The pilot was not injured and no flight plan was filed for this local post maintenance test flight. Visual meteorological conditions prevailed. According to the pilot, and FAA airworthiness inspector, who examined the aircraft and interviewed the pilot, when the pilot lowered the landing gear during approach following an engine maintenance test flight, the nose gear did not extend. After several attempts to extend the nose gear, the pilot performed a precautionary approach and landing to a dirt runway. On short final he shut off the fuel and the engine ceased to operate. The aircraft landed approximately 50 feet short of the runway in rough terrain. The airport at Alamosa, where the aircraft landed, has both dirt and asphalt runways. The pilot elected to use the dirt runway (24) due to the wind which was 240 degrees at 22 knots with gusts to 25 knots. Examination of the aircraft revealed that nose landing gear down lock spring failed and jammed the nose gear in the up position.