Bullet path, from 0 to 1000yds,
of a 175gr HPBT Sierra Mach King bullet,
fired at 2700fps of muzzle velocity.

We started off this long range shooting series with an introduction to some important terminology. Now we’re ready to apply those terms. Let’s start with an introduction on a key external ballistics concept that directly relates to long range shooting: bullet trajectory.

From the moment it leaves the muzzle, a bullet starts to follow a descending parabolic trajectory. Which means that, as the bullet travels further, the rate at which it approaches the ground increases. This parabolic trajectory is caused by gravity and drag.

In fact, as soon as the bullet exits the barrel, it begins to fall toward the ground, attracted by gravity. The amount of drop caused by gravity is a function of bullet speed. Given a distance, the higher the bullet speed, the less is the time it is subjected to the effect of gravity and the less is its drop.

This graph depicts the speed drop of the same
175gr HPBT SMK shown in the previous graph.
You can observe how the speed drops while the
bullet travels downrange.

However, bullet speed is not constant; it starts to decrease as soon as the bullet exits the muzzle due to drag, the resistance that air offers to the bullet travel. As the speed decreases, the time the bullet is subjected to gravity increases, which, in turn, increases the amount of drop. This what gives the bullet its parabolic trajectory.

The amount of drag is determined by:

Bullet speed: Drag increases when the bullet speed, relative to the air, increases.

Ballistic coefficient: Bullets with higher BC are more efficient against drag.

Air density: The higher the air density, the higher is the drag. Density of the air depends essentially on: