The Science Of Why Firing Your Gun Up Into The Air Can Be Lethal

During celebrations such as July 4th and New Year's Eve, the risk of injuries from falling bullets increases dramatically due to 'celebratory gunfire.' The age-old adage, “What goes up, must come down,” holds true for projectiles launched from the Earth's surface, as even the fastest bullets cannot escape the atmosphere. Gravity and air resistance will eventually slow a bullet down until it reaches its peak height, after which it will descend back to the ground.

The point of impact for the bullet’s return is highly unpredictable, influenced by wind and air currents. Although the bullet will descend at a significantly reduced speed compared to its launch, the potential for injury or fatality remains, particularly during celebratory events in the United States. This article explores the scientific principles behind the dangers of celebratory gunfire.

It's not difficult to understand that bullets can be hazardous. When an AK-47 fires, the bullet exits the barrel at approximately 1,500 miles per hour (about 670 meters per second), nearly double the speed of sound. Despite its relatively light weight of 0.2 ounces (around 5 grams), the energy it carries is equivalent to that of a brick dropped from a 16-story building, making it capable of causing severe injuries or death.

However, a bullet fired vertically will only strike with that initial speed if it were to land on a body without an atmosphere, like the Moon. On Earth, the presence of air resistance alters the outcome significantly.

Assuming no wind, a bullet launched straight up can reach altitudes of around three kilometers (approximately 10,000 feet) before descending. Similar to a skydiver who quickly reaches terminal velocity, the bullet will not regain its original speed. Instead, it returns to Earth at about 150 miles per hour (241 kilometers per hour), which is only 10% of its initial speed. Given the physics of energy (which relates to the square of speed), a falling bullet carries only 1% of the energy of a newly fired bullet, akin to a brick dropped from a height of just 50 centimeters (about 20 inches).

While this analysis accurately reflects the speed and energy of a bullet when it lands, the location where it lands can be up to two miles (around three kilometers) away from its point of origin. A bullet falling at 150 miles per hour is unlikely to be deadly, but two critical factors can drastically change this assessment:

1. Bullets fired at an angle can maintain much higher speeds, potentially exceeding several hundred miles per hour.
2. If a bullet has enough velocity to breach the skin, it can be deadly, with the threshold varying based on the type of bullet and the individual's characteristics.

The bullet's type plays a crucial role in determining its potential to inflict harm. Generally, the threshold for a bullet to penetrate skin is around 136 miles per hour, but this number can fluctuate significantly. Some bullets, especially those that are round and impact thick skin, can bounce off at speeds up to 225 miles per hour under optimal conditions.

Conversely, pointed or smaller-caliber bullets can penetrate skin at lower speeds. For instance:

• Buckshot can pierce skin at 145 miles per hour,
• .38 caliber bullets at 130 miles per hour,
• 9mm handgun bullets at just 102 miles per hour,
• .30 caliber bullets at only 85 miles per hour.

The ease with which skin can be punctured varies greatly among individuals and different body regions. Healthy adults generally have thicker, more elastic skin, while young children have thinner skin, and elderly individuals may have thicker but less elastic skin, making them more vulnerable to injuries. For example, skin on the upper lip is 50% thicker than that on the cheek, while skin near the cheekbones tends to be thinner, especially in older adults.

A comprehensive report by U.S. Army Major General Julian Hatcher compiled various military ballistic tests, concluding that a .30 caliber bullet reaches a terminal velocity of 200 miles per hour, sufficient to breach skin in nearly all instances.

Although it may seem improbable that a stray bullet would hit someone, numerous instances prove otherwise. For example:

• In 2010, a four-year-old boy named Marquel Peters was killed by a falling bullet in Decatur, GA.
• In 2013, a 10-year-old girl, Aaliyah Boyer, lost her life to a falling bullet in Maryland on New Year's Day.
• In 2017, Javier Suarez Rivera, 43, was fatally struck by a stray bullet in Houston, TX, just after midnight on New Year's.
• Also in 2017, Texas State Representative Armando Martinez survived being hit in the head by a falling bullet.
• On July 1, 2017, a 13-year-old boy, Noah Inman, was killed by a stray bullet likely due to celebratory gunfire in Indiana.
• In 2019, Dr. Chad Wilson's emergency room treated a woman who had a stray copper bullet removed from her head.

A study examining stray bullets found that 4.6% of all deaths and injuries were directly linked to celebratory gunfire.

While stray bullets often result from armed conflicts, a notable portion of injuries and fatalities stem from preventable celebratory gunfire. All 50 states prohibit celebratory gunfire, and in many jurisdictions, those responsible for fatal incidents can be charged with felonies. This raises the question: if celebratory gunfire is illegal, why are firearms discharged during military funerals or ceremonies?

The answer lies in the use of blanks rather than live ammunition during such events. Unfortunately, most celebratory gunfire in communities involves real bullets, leading to severe consequences. A bullet fired into the air remains a threat, with the danger persisting for up to two minutes after the gunshot.

The highest risks associated with celebratory gunfire occur in densely populated urban areas during gatherings, particularly on July 4th and New Year's Eve. Smaller, denser bullets achieve greater terminal velocities than larger ones, making them deadlier. At higher altitudes, reduced air resistance allows stray bullets to carry more kinetic energy, increasing the risk of fatalities.

The greatest danger arises from firing bullets at an angle rather than straight up, as angled shots can retain speeds sufficient to penetrate skin, posing risks to anyone in the vicinity.

Despite the ongoing threat posed by celebratory gunfire, there are positive developments. A CDC report from 2004 indicated that celebratory gunfire in Puerto Rico resulted in two deaths and 25 injuries annually; however, since 2012, efforts to raise awareness have effectively eliminated New Year's fatalities from stray bullets.

Firing a weapon into the air creates a hazard for anyone within a two-mile radius, and this risk continues for up to two minutes after the last shot is fired. Although there are no recorded cases of shooters being struck by their own stray bullets, it remains a concerning possibility. Ultimately, individual freedoms must be weighed against the safety of innocent bystanders.

Starts With A Bang is now on Forbes and republished on Medium after a 7-day delay. Ethan has authored two books: Beyond The Galaxy and Treknology: The Science of Star Trek from Tricorders to Warp Drive.