My 6.5mm CM AICS mags are all marked .308 (or 7.62x51). They work great in my 6.5mm CM bolt action.
You don't have anything to worry about with a .308 mag. That is the normal mag for a 6.5mm CM.

The only issue I have found is getting mags that leave enough space to load the 6.5mm rounds out long enough to minimize the jump.
The plastic mags have thicker front lips and limit the O.A.L. a bit more than the metal mags.
My MDT mags only let me load out to 2.895 or so.
I have two bullet types that are most accurate when loaded at over 2.910 so I have to feed those longer rounds one at a time since they won't fit in the mag.
My AICS mags feed the single rounds fine if I just rest them on the feed lips.