Answer:
They use the Accuracy International AW in 7.62x51, Stoner (Knight's Armament) SR-25 in 7.62x521 (the SR-25 is basically an upscaled AR-15, and was the basis for the US military's M110 Semi Auto Sniper System), Blaser 93 in .338 Lapua Magnum, and Accuracy International AW50 in 12.7x99 (.50 BMG)