I just went through this process of selecting a 30 caliber bullet to develop a new load for my 300 WSM and I have 2 boxes of 200 grain Accubonds in shipment right now. I have shot the 165 grain Accubonds for years, with great results on elk, sheep, deer and antelope. I tend to like a high shoulder shot, with an expanding bullet for elk. I have been wanting to to extend my effective range to around 800 yards, and still have the bullet retain around 1500 ft-lbs of energy and expand property at that range. The Accubonds appear to expand well to velocities as low as 1800 fps from what I have researched. I am expecting to have a load for the 300 WSM that will have at least 1500 ft-lbs of energy and a velocity of 1800 fps at 750 yards. You should be able to extend that range with your 30-378 with that bullet.
Now...for very long range, the current mindset seems to be a higher BC "fragmenting" bullet with a lung shot to the ribs (not a bone breaking shot through the shoulders), although that is outside of my own personal experience. Although the BC is higher on the 210 Bergers (which I already have on hand) I elected not to go with them at this time. I DO plan to develop a load for them in the future, for longer range shots (over 800 yards, hopefully with dial in corrections using the Accubonds as my primary load for shots under 750 yards). My concern with the Bergers is that they kill by fragmentation and I have heard reports (again not personal experience) that they can do some significant meat damage at high velocities. Therefore, I have been concerned what the Berger (or other fragmenting designs) would do to meat inside say 200 yards or so. That is why I chose an expanding bullet (which I have had good experience with) for shots inside 750 yards with a 300 WSM.