8mm German Mauser= 7.92x57mm. Usually a ~170gr bullet at ~2600 fps.
30-06= 7.62x63mm. M2 ball was a 150gr FMJ at ~2500 fps.
Very similar in ballistics. I have a Kar98 in 8mm and an M1 Garand in '06; and barnyard ballistics testing (ie. watermelons, water filled milk jugs, pumpkins, etc.) show both cartridges to be in the same class. Neither would be frowned upon if the need arose to defend my homeland in 1940...or for that matter, 2014
And a side note that SMG offers a version in .308; which would be my choice.