A Defender from the 355th Security Forces Squadron fires the M4A1 carbine rifle at Davis-Monthan Air Force Base, Arizona, Aug. 11, 2021. The fully automatic M4A1 carbine rifle is an upgrade to semiautomatic M4, which fires only a three-round burst. Defenders are transitioning to the new weapon, which comes equipped with a 1:6 magnification ratio Direct View Optic. (U.S. Air Force photo by Senior Airman Alex Miller)