Marines and a corpsman with Battery T, 5th Battalion, 10th Marine Regiment, take their positions along the gun line. The unit spent the day refreshing their skills with the M240-B machine gun with senior corporals and sergeants coaching their junior Marines and sailors. - Marines and a corpsman with Battery T, 5th Battalion, 10th Marine Regiment, take their positions along the gun line. The unit spent the day refreshing their skills with the M240-B machine gun with senior corporals and sergeants coaching their junior Marines and sailors.