In Vietnam a gun truck, for those who aren't familiar with them, was usually a five ton truck with heavy steel plate on the doors protecting the driver and assistant driver. On the sides, front and rear of the truck bed they installed heavy steel plate high enough to permit the troops to stand upright and be protected. Machine guns were mounted to permit the gunners to bring fire on any attackers foolish enough to take a crack at us. We didn't have any but I've heard some units mounted miniguns instead of machine guns.