On November 9, 2011, at 1134, eastern standard time, an experimental amateur built, Greiner RV-8, N220RG, registered to and operated by an individual, incurred substantial damage during landing when the right main gear collapsed at the Boire Field Airport, Nashua, New Hampshire. The commercial pilot and passenger were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the Title 14 Code of Federal Regulations Part 91, personal flight. The flight originated from the same airport earlier that day, about 1030. The pilot stated that the pleasure flight was uneventful. The wheel landing and landing roll were normal and about 1,000 feet down the runway, the right main gear collapsed. The airplane then ground looped incurring structural damage to the right wing. Further examination showed the right main gear spring attaching bolt had fractured. The passenger also reported that the landing was uneventful until the ground loop occurred. The pilot reported that the landing gear had accrued approximately 80 hours with an estimated 100 landings, and was original to the manufacturer’s kit. In a discussion with the pilot following the repair of the accident airplane, the pilot reported that a possible explanation for the failed landing gear could have been the hardware installation. The pilot received the airplane partially built with the landing gear assembled. The pilot reported that in this situation, the landing gear bolts are difficult to access. Although the pilot ensured that the appropriate torque was applied to the hardware, he stated that one of the bolts may have not been seated properly. During the rebuild of his airplane, he also identified fretting in the area. There were no photos taken of the fretting. Since the accident, the pilot uses a video borescope to conduct visual examinations of the area. Portions of the outboard and inboard landing gear spring brackets and the fasteners were submitted to the NTSB Materials Laboratory for examination. All of the fractured components exhibited features consistent with overload failure. X-ray florescence spectroscopy revealed that both landing gear spring brackets were consistent with a 4120 steel alloy.