Senior Airman Toby Gravley, a 28th Civil Engineering Squadron power production journeyman, assembles an M4 Carbine at Ellsworth Air Force Base, S.D., June 11, 2021. During the M4 breakdown relay race of the Prime Base Engineer Emergency Force (BEEF) Challenge, Airmen raced carrying two ammo cans from the starting line to a table with an M4. Once they reached the weapon, they were required to disassemble or reassemble it and return to the starting line with the ammo cans to tap in the next team member. (U.S. Air Force photo by Airman 1st Class Quentin K. Marx)