While .30-06 Frangible rounds are common, the story of their development is not well known. They were actually developed during WWII by Duke and Princeton Universities as part of a government contract. The intent was to develop a bullet that could be used to train bomber gun crews by allowing them to fire at a real aircraft. It took several years to arrive at a suitable bullet (and an armored aircraft for that matter). The common mottled grey-green bullet is actually a mixture of powdered lead and Bakelite, officially referred to as RD-42-93. Usually found with green and white bullet tips,