Lance Cpl. James Conley, a field artilleryman with 3rd Battalion, 14th Marine Regiment, 4th Marine Division, cleans the barrel of the M777A2 Lightweight Howitzer after firing rounds at Fort Indiantown Gap, Pa., during exercise Twisted Sister, a battalion fire exercise, Oct. 25, 2014. The purpose of swabbing the barrel after each firing is to ensure that the gun is sufficiently cooled so as not to prematurely ignite the next group of powder placed into the gun. (Marine Corps Photo by Cpl. J. Gage Karwick/Released)