Environmentally friendly bullets. Non toxic, and kill humans more reliably.
Why, oh why, would they waste time, money and effort on a tungsten-based bullet given that "there was no tungsten in the U.S. strategic stockpile, and the bullets, alone, would have accounted for the Western Hemisphere’s entire annual output. The world’s largest tungsten producer—China, which accounts for 88 percent—could not be relied upon in wartime."