Proponents assert that the Grendel is an ideal middle ground between the 5.56 mm NATO and the 7.62 mm NATO, taking the best attributes of each. It has a flatter trajectory and retains greater terminal energy at extended ranges than either of these cartridges due to its higher ballistic coefficient.[2]from 6.5 mm GrendelI shoot pop bottles with 5.7x48.6 at 500 yds
.30-06 was not developed from the .45-70. It may have been developed because of the -70, but the development of the .30-06 was from the .30-03, from the 6mm Lee Navy, from the .30-40 Krag, as a result of the new Mauser bottlenecks that was kickingass on the .45-70.
Ballisticly the .30-06, .308 or 7.62x51 are similar. The .308 was developed from the .300 Savage or T65 research, it is not a cut down .30-06. The reason they went with the Savage round had to do with case capacity and taper of the case for ejection in full auto fire, and political issues with Britain.