LESSON ZERO Dave Mainwright, an Australian army warrant officer, teaches U.S. Marines a different way to zero out their weapons during a data collection exercise at Marine Corps Air Ground Combat Center, Twentynine Palms, Calif., Jan. 21, 2009. The Marines are assigned to1st Battalion, 8th Marine Regiment. SHARE: Download: Full Size (0.07 MB) Credit: VIRIN: 942023-V-BVV84-702.jpg Photo Gallery