According to the Military Channel it is the CheyTac 200:
The 408 CheyTac is an impressive round. Barrett also has its .460 Barrett with similar ballistic wonders.
I’m growing more interested in long range shooting. We will see what the year brings. Doing it right requires more than just the rifle. You also have to build up loads to fit the rifle, the weather, and also be able to estimate conditions right. With that much to learn, it may become next years project.