1. Trajectory - The trajectory is the path of the round in flight (Figure 5-1). The gunner must know the trajectory of each machine gun round to effectively fire the weapon throughout its full range. For example, the path of a round is almost flat at ranges up to 300 meters; then it begins to curve, and the curve becomes greater as the range increases.
2. Maximum Ordinate - Maximum ordinate is the highest point of the trajectory between the muzzle of the weapon and the base of the target. It occurs about two-thirds of the distance from the weapon to the target. The maximum ordinate increases as the range increases (Figure 5-1).
3. Cone of Fire - When several rounds are fired in a burst from any machine gun, each round follows a slightly different trajectory. The pattern these rounds form on the way to the target is called the "cone of fire" (Figure 5-2). This pattern is caused mostly by the vibration of the machine gun and the variations in ammunition and atmospheric conditions.
4. Beaten Zone - This area (Table 5-1 and Figure 5-2) is the elliptical pattern formed on the ground or target by the striking rounds. The length of the beaten zone changes when the range to the target changes or when the machine gun is fired on different types of terrain. Shorter ranges and downward slopes produce lengthen beaten zones, and vice versa.
5. Danger Space - This is the space between the machine gun and the target where the trajectory rises less than 1.8 meters (the average height of a standing Soldier) from the ground. This space includes the beaten zone. When the machine gun is fired on level or uniformly sloping terrain at a target within 700 meters, the trajectory remains at or below the average height of a standing Soldier. When targets are engaged on level or uniformly sloping terrain at ranges greater than 700 meters, the trajectory rises above the average height of a standing Soldier. Therefore, only part of the distance between the machine gun and the target is automatically danger space.