On July 7, 2000, at 1505 hours Pacific daylight time, a North American AT-6F, N7475C, sustained substantial damage when it departed the left side of the runway and ground looped during the landing roll at Nevada County Air Park, Grass Valley, California. The airplane was being operated by the owner under the provisions of 14 CFR Part 91. The commercial pilot was uninjured and the only passenger received minor injuries. The personal flight departed Monterey, California, about 1400, and was scheduled to terminate at Grass Valley. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported he observed no wind and attempted a three-point landing. The airplane bounced slightly and, as he sat the airplane back down on the main gear, the airplane swerved to the right. He added some power and applied rudder and brake, but observed no correction. He applied full power to attempt a go-around, but departed the right side of the runway at a 25-degree angle. Approximately 200 feet from the runway the left main gear contacted terrain, swinging the airplane into a hillside.