Your 6.8 mags should work just fine, if they work OK in your 6.8.
What Greg said is, that if you have to buy mags, get the 6.5, because they can also be used on so many other calibers that you may want to get in the future. I think that I also saw a post previously, where R. Johnson (Richie) said to get 6.5 mags for the same reason, but I could not find where I saw that post, so I ordered 6.8 mags, to be sure that I had something that would work when my 6x6.8 upper arrives. I will be ordering 6.5 in the future, because I am also looking hard at the 243 LBC and I don't have any plans to get a 6.8
I messed up with the calender when I said Monday (must've been wishful thinking. It arrived at the office today. Can't get out until Saturday anyway so I only lost one evening of tinkering with which scope to mount etc.
Out of the box it looks awesome. Can't mess with it much at the office so I'll try and post a picture once I have it on a lower with scope.
Fired up to get it out in the field Saturday. If I can get zeroed quickly I am calling in Coyotes Sat evening.