hopefully i was mistaken. phew... http://www.geforce.com/whats-new/articles/nvidia-geforce-310-54-beta-drivers-released NVIDIA drivers for AC3 and BO2.
from my research there are more like hundreds of versions. And that version right there is definitely a 7.62 x 54 mm. an easy way to tell is by the more bent/curved magazine
Actually the chest is still off. Wrote a post about pec construction a while ago in another thread: http://www.polycount.com/forum/showpost.php?p=1946653&postcount=54