The author seems to suggest the 6.8 SPC.
Today’s military faces a more daunting threat.
Rules of Engagement which transform war fighting into self-defense constraints more severe than those imposed on civilians at home.
As for the cost of aircraft, we need the politics out of the design requirements process, and a funding profile that allows for an orderly development and test process, leading to production in economic order quantities.
6.5 Grendel is superior to the 6.8spc, but either is better than the 5.56.