I would agree with Shaggy, and go for the .22 MGs. HKMP5SD made a very important point, "lean into it". Another factor that I did not see mentioned is body size.
For a battle rifle, I'd say the M-16, 5.56/.223. I've had the misfortune of getting plenty of experience with it in Vietnam. Big or small, if you lean into it, it's controlable.