Matching ballistics between 6.5G and 308 Win

[BKKJ]

Thanks all for the replies, I'm going to mess around with ballistics calculators a bit. Going to pick up a group buy 18 and hoping it settles in around 2500fps for most loads. am still waffling 308 or 6.5 Creedmoor on the AR10 build. Mostly due to plinking ammo cost. Also (to tie back into the original post) because I'm not sure what barrel length I want yet. Was entertaining either an 18 or 20 in 308. Probably would just go 20 in Creedmoor. I'm sure I don't "NEED" better ballistics than the 308. I'm just trying to decide if it's better to keep ballistics similar while upping energy or pay a little more and improve ballistics (that are already likely good enough) as well.