What 6mmAR can do:
https://www.youtube.com/watch?v=vyckbqpqcDI
Granted, this is from a longer gun rather than a carbine, but it does illustrate the point that ammo tech has improved remarkably.
Have to second the 6mm (the round the 6.5 wanted to be) as the superior choice, particularly in the "6mm Turbo II 40" (Ackley Improved) or "6mm Grinch" configurations (my understanding is that the Turbo Imp. and the Grinch are interchangeable, as both are based on necked Grendel brass with...