The pilot flew to Greensburg, where he brought the helicopter to a 2 ft hover and departed with a max performance climb. He stated the helicopter began to exhibit control irregularities which he described as 'a Dutch roll wobble type of shuffle.' He continued the flight and said the 'shuffle' subsided as power was reduced during approach to Mt Pleasant. However, he experienced directional control problems during the approach which were proportional to changes in collective and throttle applications. Initially, he thought the problem was associated with the wind. The pilot increased throttle, collective, right pedal, and began a climb. Then as a precaution, he cut the throttle to stop an increasing vibration and keep the engine from overrevving. Collective was reduced to maintain rotor RPM, then was increased on descent through 20 ft AGL, but the aircraft landed hard, collapsing a skid. According to witnesses, it had insufficient power and made a 360 degree rotation before impact. Two main rotor blades separated and were found within proximity of the helicopter with impact damage.