Sgt. 1st Class Marc Westenbarger, tank commander, C Company, 1st Battalion, 77th Armor Regiment, 4th Brigade Combat Team, 1st Armored Division, uses a muzzle boresight to zero his crew’s Abrams 120mm cannon May 10 prior to a night live-fire event during the Sullivan Cup precision tank gunnery competition at Fort Benning, Ga. Boresighting the cannon ensures that the tank’s computer-based aiming system is properly aligned with the cannon itself, providing crew members with accurate round placement.