The rifle in the video is 5.56, google travis haley najaf rifle.if you or anyone you know has an M1A- I'd love to see a comparison. the .308 when combined with an accurized and properly bedded barrel makes for a sweet precision rifle system. When you use a high capacity semi auto rifle like an M1A or AR-10, it makes for a great backup sniper rifle. Accurate enough to reach out far- and fast enough to open up a whole case of whoop-ass when you need to.
I believe this merc is using an AR-10. The magazines might just look larger cause theyre closer to the mag, but I think they're 308. at 1:35 radio chatter from his spotter says that there are bad guys at about 800 meters, and that he cleaned them out.
YouTube - Blackwater Sniper
I am looking to venture into the AR-10 world, I have heard good things about the DPMS G2 rifles. Still have to get my hands on one which is tough given the state I live in...may want to check them out as well.