The military's selection of the 5.56x45mm has less to do with its lethality or wounding potential than it does weight and higher rates of fire that can only be sustained logistically with lighter cartridges. My basic load when I was a 1985-1991 was 390 rounds loaded in magazines and one bandolier in my ruck. It'd have been half that if I'd been issued an M-14, even less if it'd been a Garand.