Different proprietary specifications for the same round: The HK G28E CSASS (top) and Colt 901 CSASS (bottom). Any contract for a standard rifle firing a round with a longer overall length than the current 5.56mm would necessarily have to be sole-source, making the US Army dependent on a single manufacturer for all their future individual weapons. This would repeat the mistake made when the US Army allowed Colt to retain exclusive rights to the M4 Carbine.