The pilot stated that the fuel gauge read 74 gallons during his pre flight inspection and that 10 minutes after takeoff, when he was about half way to his destination, it was reading 24 gallons. He further stated that when he was about 5 miles from the destination the boost pump lights came on and the gauge was reading 5 gallons. He stated that at that point he decided to execute a precautionary landing and find the problem. The engine flamed out due to fuel exhaustion before he could land and he entered autorotation. During the descent the pilot noticed that he was going to hit a bush and he extended his glide over the bush. As a result the aircraft landed hard in a tail low attitude. Investigation revealed that the pilot had not visually checked the fuel during the pre flight and that the aircraft had 20 gallons of fuel on board when he departed on the accident flight. All of the fuel system components, including the fuel gauge were functionally tested and operated normally.