For those of you that haven't loaded the 6.8 much yet, after reading all of the posts above, I suggest you take this from them:
1) loading to 2.30" is the maximum that can be achieved with PRI mags, and this COAL will not fit in all mags. That's very important. Don't take away form this the idea that you can load to 2.30 and use these rounds in all mags.....you can't. Its a shame, but you can't.
2) Loading close to the lands is a technique which can increase accuracy. It makes perfect sense, because if the bullet is not perfectly aligned with the axis of the cartridge, then it will tend to "knock around" against the sides of the forcing cone( throat) as it enters the rifling, and could be malformed slightly. This could lead to a loss of bullet to bullet consistency, i.e accuracy.
3) However, in AR style rifles, these principles are mitigated by a few things. First, the mag issue, as mentioned. If you are in combat, accuracy is moot if you rifle will not fire. You could get dead in a hurry that way. Second, not all rifles will feed the longer rounds the same way. So, Paulo has a good point, in that, until you have tested every rifle you own, thoroughly, with rounds of this length, you cannot be 100% sure that they will feed like rounds which are slightly shorter.
4) the shape of the bullet will also determine whether "loading long" is a good thing or not. I already mentioned that the Nosler Accubond was not accurate for me loaded all the way to 2.30. It had to be taken back to 2.29". Also, contrarily, you cannot load the Barnes TTSX to any length other than 2.30" ....it is just too long. That is the only length that allows adequate case capacity and for the bands and ogvie to be oriented properly in the case for accuracy and good seating.
Having said all the above, JamesB has hit on something. Since we are in a time when many of you has to depend upon the anecdotal evidence that some of us "experts" post about the 6.8 and loading it, you must also test for yourselves, to find what works best for you. You must also decide what situations are going to determine the priorities you set for loading ammo.
I hunt with my AR's so, loading to 2.30 or even 2.305" works fine, gives what I perceive to be better accuracy and allows me to get max velocity with the least compression %. Anecdotally, I will also say, that with PRI mags, I have never, ever had feeding issues with any of my 6.8 rfles. In fact, I am astounded at the utter 100% reliiability, even with hand loads.