Here's what I'm thinking
Well, it can be used if you wish, but...
But the FCD depends upon the shoulder to actuate the collets, which means that the length of the case neck matches the height of the collet. The 30-06 case neck is about 0.380" (depending upon your chosen trim-to length) where the 308 is about 0.340".
Go ahead and try it if you already own one, but look down into the top of the die while crimping and look to see if the collet is closing on the case mouth firmly.