I just found this article with some images wich may interest the one or the other:
very interesting, thanks Alex
The latest info is that Textron have carried out a “Caliber Configuration Study” analysing the pros and cons of different calibres and bullet shapes from 5.56mm to 7.62mm, and have concluded in favour of a 6.5mm firing a low-drag bullet. They are now developing this CT round in parallel with a carbine to fire it. This is in addition to the 7.62mm CT MG and is expected to be ready for testing in the same time-frame (mid-2016). It will be interesting to see how this develops.