User blog comment:Cod1/U.S. Marines with AK-47s/@comment-1080767-20100409002535

The 7.62 is overkill when it comes to mid-range anti-personel combat. A lighter and faster round would be perfect for this battle rifle role, but the 5.56 that NATO designed sacrifices too much stopping power, and so it often won't fully kill a target. If you find the exact dimension that would be between the 7.62 and 5.56's diameter, you'd find something like 6.6. And that's where the 6.8 SPC comes into play.