The pilot reported that he was drifting left toward the runway turnoff following a successful landing on runway 33. The winds were reported from 040 at 8 knots, with occasional gusts to 12 knots. As the aircraft neared the turnoff, it suddenly and sharply ground looped to the right. During the ground loop, the left main landing gear collapsed. The aircraft was inspected by an FAA inspector, who found no evidence of fatigue or corrosion. The airplane was equipped with oversize tundra tires.