The saying "What goes up must come down" is an appropriate starting point. If you fire a gun into the air, the bullet will travel up to a mile high (depending on the angle of the shot and the power of the gun). Once it reaches its apogee, the bullet will fall. Air resistance limits its speed, but bullets are designed to be fairly aerodynamic, so the speed is still quite lethal if the bullet happens to hit someone. In rural areas, the chance of hitting someone is remote because the number of people is low. In crowded cities, however, the probability rises dramatically, and people get killed quite often by stray bullets.
Here's one example: On New Year's Eve 2017, Democratic member of the Texas House of Representatives Armando Martinez, stepped outside a home and suddenly felt as if he'd been struck with a sledgehammer. After he was rushed to the hospital, it turned out that he'd been struck on the top of the head by a falling .223-caliber bullet. A fragment of the round penetrated the top of his skull and lodged itself in the top layer of his brain, requiring surgery to remove it, according to CNN.
Martinez, who recovered from his injury, became another victim of the strange custom of celebratory gunfire, in which revelers fire bullets into the air that eventually fall back to Earth — and occasionally hit other people.
There aren't good statistics on how often this happens across the U.S., but news reports describe numerous fatalities over the years. This 2015 article from The Trace, for example, describes two cases of children killed by falling bullets apparently fired during Fourth of July celebrations in 2011 and 2012. A 2004 study by the Centers for Disease Control and Prevention found that on New Year's Eve and New Year's Day of that year, bullets from celebratory gunfire caused 19 injuries and one death. Thirty-six percent of the victims were struck on the top of the head, with feet (26 percent) and shoulders (16 percent) the next most common injury sites. A 2017 Miami Herald article cites numerous instances over the years, ranging from at least 20 people killed in Iraq in 2003 by celebratory gunfire after the death of Saddam Hussein's sons Uday and Qusay.
So How High Will a Bullet Go?
Aside from the perplexing question of why such a reckless, potentially lethal practice remains so popular, you may also be wondering, what actually happens to a bullet that's fired straight up into the sky? How high does it go? What stops it and sends it falling back to Earth? And when it descends, when and where does it land?
Those aren't necessarily simple questions to answer. Ballistics researchers have spent a lot of time studying the performance of bullets fired horizontally, because that's useful information for improving the accuracy and range of shooters. But when it comes to firing straight up in the air, which isn't something that soldiers, police officers, hunters or target shooters normally would do, there's not nearly as much data.
U.S. Army Maj. Gen. Julian Hatcher, who apparently was curious and had some time on his hands, did experiments in Florida in which he fired various weapons — ranging from rifles to machine guns — up into the air, and tried to measure how long it took for the bullets to come down, as well as where they landed. As he noted in his 1947 volume "Hatcher's Notebook," he calculated that a standard .30 caliber bullet fired from a rifle pointed straight up would rise to an altitude of 9,000 feet (2,743.2 meters) in 18 seconds, and then would return to Earth in another 31 seconds, and during the last few thousand feet would attain a "nearly constant" speed of 300 feet (91.4 meters) per second.
But ballistics researcher James Walker, who holds a doctorate in mathematics and is department director of engineering dynamics at the Southwest Research Institute in San Antonio, says that the altitude attained by a bullet fired straight up would depend upon the type of weapon and projectile, just as it does when fired horizontally. A handgun, which has a shorter barrel than a rifle and fires ammunition with a smaller cartridge that doesn't contain as much powder, isn't going to send a bullet soaring as high as a rifle will. Different types of rifles and ammunition vary as well.
"With a .22, which isn't a big-game rifle, the cartridge is the same diameter as the bullet," Walker explains. "It doesn't have that much powder, and that bullet doesn't go fast. Rifles like the .30-06 have a much larger cartridge, which will go faster because there is more powder to burn."
When fired horizontally, bullets tend to slow down rapidly due to air drag, so that a rifle bullet may be down to half of its initial speed by the time it gets to 500 meters (1,640.42 feet), Walker says. "If you choose to shoot it up, it will slow down faster because of gravity, not a whole lot."
For altitude estimates, Walker pointed to this chart on the website of Close Focus Research, a ballistics testing company, which shows that a .25 caliber ACP handgun bullet might reach a maximum height of 2,287 feet (697 meters), while a .30-06 rifle bullet would rise to 10,105 feet (3,080 meters).
What Goes Up...
But no matter how high a bullet goes in the air, however, eventually it will decelerate until its velocity reaches zero, at which point it will begin to fall back to Earth, as detailed in this 2018 article on falling bullet injuries in the Journal of Neuroscience Rural Practice.
"Again, the height up is a non-issue as to the speed down, as the bullet (if no longer spin stabilized) will hit a terminal velocity based on its shape, orientation, and whether or not it is tumbling," Walker explains in a follow-up email.
And most importantly, a bullet is unlikely to fall straight down, as wind can alter its path, Walker says. That makes it difficult to predict where a bullet will land.
Back in Texas, Representative Martinez sought to keep others from being hit by falling bullets, by introducing legislation raising the penalties for discharging a firearm without an intended target, according to The Monitor. So far, he hasn't been successful, but he reportedly plans to try again in 2019.