It's 2017. We are talking about hunting with an AR. Can we leave subjectively designed "power factor" calculations to the past. They were all designed to agree with the bias of a person who never heard of bonded or all copper bullets, and never shot gel. I personally have zero interest in hunting with conventional bullets in this smaller class of calibers.

The velocity a bullet will still open at, plus have enough penetration is an objective number. One we have through testing for a lot of bullets.

The simple truth is that there is not enough difference between the 6.8 and 6.5 to matter at hunting range. I would feel good with either, and have a hard time finding a real reason to change from the one I had.

And don't buy the SPC II hype either. 5-10 percent is the chamber, the rest is handloading to "pressure signs".