I thought the doctrine of old as with the 5.56 round it was for controllable fire by the weapons user more accurate fire and less being belted around from say dumping a 20 round mag from a M-14 in 308.
With regards to the 6.5 there will be a substantial bang probably not as much recoil as a 308 but being able to control the POA under high cyclic rates of fire whether full auto or semi will need to be seen I know my 6.5 makes a hefty report and thats with a 30" barrel a 13" barrel well you wont want to be close together!
Reminds me of the Germans in WWII with the Kurtz round looking for an alternate round for the troops so accurate fire in a semi auto can be applied.