The ONLY things that matter are bullet construction and impact velocity. That should be your only concern. And you basically have a constant bullet construction with using copper. So at the end of the day, you only need to focus on your impact velocity. I crunched a few numbers and 308 velocities are on the edge of your minimal expansion threshold at 400 yards.
Do you have a specific 130-165gr bullet or factory offering in mind that you prefer to use?
Federal Trophy Copper 165 grain is what I've been using for 308.