Interior and Exterior Ballistics

What happens during the short period between firing and impact on the target?

The cartridge's design, gunpowder, and the bullet create optimal internal and external ballistics. The crucial factor for precision and effectiveness is the bullet – its design and weight are critical factors for the trajectory.

Interior Ballistics

Interior ballistics is a term that describes the events from the ignition of the primer to the moment the bullet leaves the barrel. It is extremely important that ignition and combustion are consistent from shot to shot. We combine the right primer with the right powder in each load. Gas pressure is maintained within specified limits while optimizing the balance of precision, velocity, and recoil.

After firing, it takes about 0.005 seconds for the firing pin to reach the primer. The pin makes a circular impression on the primer and ignites its composition, propelling the cartridge forward by approximately 0.1 mm. Hot gases and glowing particles pass through the primer hole into the cartridge case, igniting the powder.

Increased pressure propels the bullet forward. When it reaches maximum pressure, it attains a velocity of 300 m/s. From the primer's ignition, it takes 0.0015–0.002 seconds for the bullet to exit the muzzle. As the bullet exits, it is surrounded by hot gases that continue to accelerate it for a few more centimeters. Due to the barrel being slightly inclined upward, the trajectory starts about 3–5 cm below the line of sight.

The rifling in the barrel causes the bullet to spin. Longer bullets require a faster rotation than shorter ones. Rifling twist rates typically vary between 8" (20.3 cm) and 16" (40.6 cm) depending on the caliber. It's also crucial to minimize barrel wear to protect it. Additionally, the powder must burn completely, leaving no residue in the barrel. Both of these can be guaranteed through a well-thought-out design concerning the cartridge case, bullet, and powder.

Exterior Ballistics

The behavior of a bullet after it leaves the muzzle is the domain of exterior ballistics.

External ballistics can become complex if desired. For example, during World War I, the Germans fired upon Paris from a distance of 120 kilometers using a cannon, with the trajectory reaching 30 kilometers at its highest point above the Earth. The bullet's time in the air was so long that one had to account for Paris's movement due to the Earth's rotation – which involved a fair amount of mathematics. However, when a hunter takes a shot at an elk within 100 meters or less, no mathematical calculations are needed; it's simply a matter of aiming. Readers should not be intimidated by technical terms.

Gravity and Trajectory

Imagine firing a rifle bullet over a calm body of water, perfectly parallel to the surface. If, at the exact moment the bullet leaves the muzzle, you also drop the same type of bullet straight down from the same height, both bullets will hit the water's surface simultaneously. This occurs because gravity pulls them downward with the same force whether the bullet is in motion forward or not.

On very short-range shots, the bullet is in motion for just a fraction of a second and does not fall very far. This is why the trajectory is flat at short shooting distances. At a shooting distance of 300 meters, the time of flight – meaning the time the bullet needs to reach the target – is roughly half a second, during which the bullet falls quite a bit.

Speed and Shape Matter

A fast bullet has a flatter trajectory than a slow one simply because it reaches the target more quickly and therefore has less time to fall. A pointed bullet has a flatter trajectory than a blunt one because it is less affected by air resistance and reaches the target in less time. However, at the same time of flight, both a pointed and a blunt bullet fall the same distance.

When the shooting distance varies significantly from what is expected, the hunter must adjust their aim accordingly – either higher or lower – or make corresponding adjustments to the scope. At typical shooting distances, the bullet hits the target precisely as intended. Higher bullet velocity and a higher ballistic coefficient result in less deviation due to crosswinds.

Thanks to the bullet's optimized trajectory and unique design, it is tailored for specific hunting requirements. NORMA allows hunters to focus on the hunt without worrying about ammunition ballistics. High-quality production standards ensure reliable and predictable bullet performance both inside and outside the rifle barrel.

It's important to note that consideration should always be given to what lies behind the target, as bullets can travel several kilometers and cause damage.