On July 21, 2012, about 0915 mountain daylight time, an experimental amateur-built Herem DR-107 airplane, N58GH, collided with terrain while maneuvering after takeoff from the Bridger Municipal Airport (6S1), Bridger, Montana. The commercial pilot, the sole occupant of the airplane, was seriously injured. The airplane impacted terrain in a tail-low attitude and sustained substantial damage to both wings and empennage. The airplane was registered to, and operated by, the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and no flight plan was filed for the cross-county flight; the pilot's planned destination was Billings, Montana. The pilot was participating in a general aviation fly-in at the Bridger Municipal Airport. He arrived earlier in the day, and the accident flight was the return leg to Billings. A witness stated the pilot's takeoff and initial climb appeared normal; however, when the airplane reached midfield it rolled left. The airplane continued to roll, and about 270-degrees through the second roll the airplane pitched up. The airplane returned to a nearly level pitch attitude and then pitched down and subsequently collided with terrain. The pilot reported that he did not intentionally roll the airplane after takeoff; however, he was unable to recall specific details regarding the sequence of events leading up to the accident. Examination of the wreckage at the accident site by a Federal Aviation Administration (FAA) inspector revealed that the airplane came to rest near the departure runway and sustained substantial damage to the fuselage and both wings. Examination of the airframe, engine and flight control system components revealed no evidence of a preimpact mechanical malfunction or failure that would have precluded normal operation. The NTSB Pilot/Operator Accident Report (form 6120), submitted by the pilot, he indicated that there were no mechanical malfunctions of failures with the airplane.