3.7 Maximum Height of Fire of a Gun
The maximum height, or maximum altitude, that a bullet will reach if fired straight up is also a concern in the design of outdoor shooting ranges. If a bullet can rise to an altitude at which it could threaten aircraft over the shooting range, or upon returning to earth threaten local residents or property, then reinforced roof barriers must be placed above the firing lines to prevent accidental discharge of bullets in an upward direction. The maximum height that a bullet can reach depends on shooting conditions, especially on the altitude of the firing point and also on atmospheric conditions at the firing location.
Infinity can be used to closely estimate the maximum height that can be reached by a bullet from any cartridge. The maximum height computation capability in Infinity is reached by selecting the “Vertical Fire” entry in the “Operations” dropdown menu. For the cartridge, load and shooting conditions of interest, a reference trajectory need not be calculated. However, those conditions must be entered in the “Trajectory Parameters” and “Environment Parameters” lists in the sidebar that appears on the monitor screen in the “Trajectory” operation. After those conditions are entered, the user can proceed directly to the “Vertical Fire” operation. Key parameters for the “Vertical Fire” operation appear in a sidebar in this mode and can be changed to examine the effects of varying any of these parameters. When a vertical fire trajectory is calculated, the monitor screen displays a message that states the maximum height the bullet will reach above sea level and above the firing point, taking account of the firing point altitude. The message also states the flight time of the bullet to reach the maximum height.
Bullets can reach great heights if fired straight up or nearly straight up. This is especially true for rifles firing magnum cartridges. But bullets from rifles firing standard cartridges or from handguns are capable of reaching significant heights. For example, a 300 Winchester Magnum cartridge with the 180 grain SBT GameKing bullet at 2800 fps muzzle velocity fired from a point 500 feet above sea level with standard atmospheric conditions will reach a maximum height of 11,993 feet (2.27 miles) above the firing point, which is a maximum altitude of 12,493 feet above sea level. A 30-30 loaded with the 150 grain FN Pro-Hunter bullet at 2200 fps fired from the same location will reach a maximum height of 7232 feet (1.37 miles) above the firing point, or 7732 feet above sea level. A 45 ACP loaded with the 230 grain FMJ Match bullet at 850 fps fired from the same location will reach a maximum height of 4198 feet (0.8 mile) above the firing point, or 4698 feet above sea level.
If the firing point altitude is changed to 5000 feet, the 300 Winchester Magnum bullet will reach a maximum height of 12,707 feet above the firing point, a maximum altitude of 17,707 feet. The 30-30 bullet will reach a maximum height of 7637 feet, an altitude of 12,637 feet. And the 45 ACP bullet will reach a maximum height of 4465 feet, an altitude of 9465 feet. These numbers show that a bullet will travel upward considerably farther when air drag decreases (because the air is less dense). The flight path altitudes of aircraft are referenced to sea level, of course, and so the maximum altitudes of the bullets become very important for aircraft safety considerations.