VIDEO: Self-Guided Bullet Spots, Steers and Nails Its Target. “Each self-guided bullet is around 4 inches in length. At the tip is an optical sensor, that can detect a laser beam being shone on a far-off target. Actuators inside the bullet get intel from the bullet’s sensor, and then “steer tiny fins that guide the bullet to the target.” The bullet can self-correct its navigational path 30 times a second, all while flying more than twice the speed of sound.”