There's a few great 6mm rounds in the 6mm family. The 6mm is one of them. I would like to see a 6mm x 39mm and a 6,5mm x 39mm tested just to see what they can do in performance. Sounds like a wildcat round 6,5mmx39mm or even the 6,5mm x 45mm??
Overall i think we hit a good "size" range between the 6mm to 6,5mm family