Supposedly it allows engagements at longer ranges than the 5.56mm. It uses a necked down 7.62 x 51 mm case. My thought is, if they wanting longer range engagements, why not use the 7.62 x51? Its already developed, adopted, and available. Yeah the 6.5 might give incremental improvements, but is it worth the millions in developmental costs? Personally, I think its just the military-industrial complexes way of sucking more cash from the government tit.