On May 18, 2005, at 1944 eastern daylight time a Cessna R182, N6149S, sustained minor damage following a nose gear collapse during landing roll at the Allegheny County Airport (AGC), West Mifflin, Pennsylvania. The certificated private pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local personal flight which was conducted under 14 CFR Part 91. According to the pilot, the purpose of the flight was to practice commercial pilot maneuvers. He reported that he completed the preflight inspection, engine run-up, taxi, and takeoff with no anomalies noted. The pilot departed the airport on a southwesterly heading, and flew to a local practice area where he completed several maneuvers. He then configured the airplane for a steep spiral maneuver, and moved the landing gear handle to the down position. The pilot observed the left main landing gear as it descended and locked in the down position. The green gear-down light for the main landing gear was illuminated, while the gear-down light for the nose landing gear was not. The pilot attempted to troubleshoot the system by cycling the landing gear "3 or 4 times," and checking the "press-to-test" function of the landing gear light, which was operational. He then attempted to lower the landing gear manually, without success. The pilot then maneuvered the airplane back to the airport, and advised the tower controller of the airplane's status. The pilot then performed a normal landing to runway 31, and the airplane rolled out on all three landing gear. While decelerating through approximately 40 knots, the nose landing gear collapsed, the propeller struck the runway, and the airplane slid to a stop on its nose. The weather reported at the Allegheny County Airport, at 1953, included clear skies and winds from 350 degrees at 5 knots. The pilot held a private pilot certificate with a rating for airplane single engine land and instrument airplane. His most recent Federal Aviation Administration (FAA) second-class medical certificate was issued September 13, 2004. His most recent flight review was completed March 27, 2004. The pilot reported 398 total hours of flight experience, 14 hours of which were in make and model. The airplane was examined at the scene by an FAA aviation safety inspector. The airplane was then moved to a hangar and placed on jackstands. On May 19, 2005, the FAA inspector completed an examination of the nose landing gear. The examination revealed that a downlock actuator pin on the nose landing gear actuator had worked partially out of its clevis half. The pin contacted the actuator arm piston, and prevented the full travel of the nose landing gear to the down and locked position. On August 5, 2005, the downlock pin halves from the nose landing gear actuator were examined at the Safety Board's Materials Laboratory in Washington, D.C. The examination revealed that the pin cracked/fractured due to fatigue. On December 29, 1995, the Cessna Aircraft Company published a service bulletin entitled "Nose Landing Gear Actuator Downlock Pin Inspection." According to the bulletin, the initial inspection "should be completed within the next 200 hours of operation or 12 months, whichever occurs first... After completing the initial inspection, repeat at each gear retraction check not to exceed 200 hours of operation." If a loose pin was discovered during the recurring inspection, the installation of part number SK210-155 was required. The part was actually a kit, which contained new actuator downlock pins, roll pins, and further required modification of the actuator clevis to accommodate the new pins. After installation of the new parts kit, the recurring inspection was no longer required, per the service bulletin. Examination of the maintenance logbooks for the accident airplane revealed no documentation for the recurring inspection. A examination of the nose landing gear actuator clevis revealed that the modification and installation of part number SK210-155 had not been performed. Cursory examination of the FAA Accident and Incident Database revealed over thirty nose-gear collapses attributed to the actuator downlock pins on similarly equipped Cessna airplanes. Two of the three Service Difficulty Reports (SDR) that were reviewed revealed broken downlock pins on landing gear that had been modified per the Cessna Service Bulletin.