The pilot was landing at a remote dirt/grass airstrip where the winds were gusting and variable in direction. Although the touchdown was normal, as he made rudder and brake inputs to maintain directional control, the right main gear leg separated from its mounting structure, and the right wing sustained substantial damage when it contacted the terrain. An inspection of the gear leg attachment hardware determined that the nut on the gear leg attachment bolt had been stripped from the bolt, thus allowing the bolt to come out of the attachment structure. During the pilot's initial contact with the NTSB Investigator-In-Charge, the pilot stated that the airplane's right brake had failed during the landing roll, but in a follow-up interview the pilot stated that he believes that the brake was working fine until the moment the gear leg separated from its mount.