There was no air/ground radio service at Bagby so, before landing, the pilot checked the surface wind at a nearby airfield; it was from 240º at 10 kt. He was very familiar with Bagby and had landed a Chipmunk there six times in the previous four days. On this occasion, he elected to take advantage of the 2.6% upslope on Runway 06 and land downwind. He knew the landing distance required was sufficient, given the grass surface was short and dry, but stated he would have used Runway 24 if he thought the wind was stronger than 10 kt.
A normal approach was flown to a three-point landing and the pilot held the control stick fully back as the aircraft slowed. He maintained directional control using differential braking until, at a speed of 20-25 kt, the aircraft swung left and would not respond to further application of right brake. It veered off the runway and the pilot was unable to halt it before the right wing and tailplane struck a hangar. He made the aircraft safe and vacated without assistance.
The pilot concluded that the swing to the left may have been due to the wind gusting or shifting direction.