The private pilot had recently built the tailwheel-equipped experimental airplane and had accrued approximately 20 hours (all flight instruction) in the airplane. A commercial pilot accompanied the pilot on the flight. During takeoff from Runway 12 (4,165-foot long by 75-foot wide asphalt runway), the airplane became airborne briefly and then settled back on to the runway, followed by a couple of hard bounces. Following the second bounce, the left main landing gear wheel separated and the airplane ground-looped. The airplane then rolled to the right, exited the runway, and nosed over. The pilot reported a total of 70 flight hours, but had not flown since 1951. A review of FAA records revealed that the commercial rated pilot held a flight instructor rating; however, it had expired in 2004. Examination of the airplane revealed no pre-mishap discrepancies. The winds at the time of the mishap were reported from 100 degrees at 7 knots.