Rifle bullets can exit the barrel at speeds exceeding 4,300 km/h, fast enough to cover the distance equivalent to 11 football fields in just one second.
The design of the bullet, whether pointed or round, plays a crucial role in determining its velocity. (Photo: Brais Seara/Getty)
Several factors influence the speed of a bullet fired from a gun. These factors can be categorized into two main types: internal ballistics (including propellant type, bullet weight, shape, and barrel length) and external ballistics (which includes the forces of wind, gravity, and trajectory acting on the bullet as it moves through the air). Both can be further classified into a third type, known as terminal ballistics, which describes the behavior of the bullet upon impact with a target.
According to forensic scientist Michael Haag, a bullet consists of a primer that ignites the propellant when struck by the gun’s firing pin. This ignition generates pressure that propels the bullet forward. Most bullets are made from heavy metals like lead, encased in copper, as their mass helps them maintain momentum. To illustrate, Haag compares throwing a table tennis ball and a golf ball. Both leave the thrower’s hand at the same speed, but the golf ball, due to its greater mass, travels farther.
Once ignited, the gunpowder burns rapidly, producing gas that pushes the bullet down the barrel. As it moves toward the muzzle, the bullet rubs against the barrel’s walls, generating a small amount of friction. However, guns with longer barrels can produce much faster shots.
“The barrel is indeed the greatest limiting factor for speed. The longer the barrel, the more distance the gas has to increase velocity, and the faster the bullet exits the barrel“, explains Stephanie Walcott, a forensic scientist at Virginia Commonwealth University.
For this reason, rifles typically deliver the highest speeds. Rifles are designed for use at long distances. Bullets fired from rifles can travel over 3 km. To achieve such shots, rifle bullets are aerodynamically designed to be longer, thinner, and heavier than handgun bullets. Gun manufacturers sometimes add spiral grooves in the barrel to make the bullet spin, which stabilizes its horizontal flight.
These features allow rifle bullets, such as the Remington 223, to exit the barrel at speeds of up to 4,390 km/h—fast enough to cover the distance equivalent to 11 football fields in one second. In contrast, a bullet from a 9 mm Luger handgun would only travel half that distance at a speed of 2,200 km/h.
A high-speed photo shows a bullet firing from a handgun. (Photo: Wikimedia Commons/Niels Noordhoek)
Walcott notes that immediately after leaving the muzzle, the bullet begins to decelerate. This is due to Newton’s first law, which states that an object in motion will remain in motion unless acted upon by an external force. Among the forces acting on the bullet upon firing are air resistance, gravity, and gyroscopic motion. Over time, the first two forces will overcome the bullet’s tendency to maintain a stable spinning motion, causing it to start falling. Every bullet has a ballistic coefficient, which indicates its ability to overcome air resistance and travel forward—determined by its mass, area, drag coefficient, density, and length. The higher the ballistic coefficient, the better the bullet’s capability to pierce through the air.
“But very quickly, gravity and air resistance will begin to act and slow the bullet down. The bullet will travel quite straight for a time, then start to drop and become more susceptible to environmental influences,” Walcott explains.
