Originally Posted by JonM
30-06 has a very slight edge due to a bigger case capacity so it can reach a scootch farther. The real advantage in 30-06 vs 308 comes in using bullets heavier than 168 grains. The bigger case capacity of the 30-06 really starts to shine and totally leaves the 308 behind when you get to 175-220 grains.
168 and down there is no practical difference.
But if it is strictly for targets the grain shouldn't matter much. I guess thats why the 30 06 is a widely used hunting cartridge.