Actually, I think .308 and 30-06 are essentially the same round. The 30-06 was developed from the 45-70 of which the gummint had plenty o brass around at the time so it made sense to use it and the slower burning powders of the day needed the space. More modern powders (50 yr ago) burned faster and took less space to develop the same pressure so the .308 Win was developed to take advantage of that "empty space" that is in most 30-06 nowadays. At least that is what I understand happened. Look at the ballistics, they are the same bullet at about the same muzzle vel.
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