The Shape of a Flight Path
Every projectile follows a curved path called a trajectory. From the instant it leaves the barrel, gravity pulls it downward at a constant acceleration while forward velocity carries it toward the target, producing an arc that closely resembles a parabola. Reading that arc correctly is the core skill behind interpreting any drop chart.
Bullet Drop
Bullet drop is the vertical distance a projectile falls relative to the extended bore line over a given distance. Because gravity acts continuously and the projectile keeps losing forward speed to drag, drop grows faster than the distance itself, so the amount of fall between 300 and 400 yards is far larger than between 100 and 200 yards.
Line of Sight Versus Line of Bore
The sighting system points along a straight line of sight, but the barrel is tilted slightly upward relative to it. The projectile is actually launched above horizontal, arcs up through the line of sight, reaches a high point, then descends back through it. Distinguishing these two lines explains why a projectile can strike above the aiming point at mid-range.
Zero Distance
A zero is the distance at which the trajectory crosses the line of sight on its way down, aligning point of aim with point of impact. Because of the upward launch angle, most trajectories also cross the line of sight once at a short "near zero," rising above it in between, before returning at the "far zero."
Time of Flight
Time of flight is the elapsed time from muzzle to target, and it is the true driver of drop. Gravity produces fall proportional to the square of that time, so anything that lengthens flight time, such as a lower muzzle velocity or a less efficient projectile, deepens the drop disproportionately.
Worked Example
Imagine a rifle zeroed at 100 yards. At 200 yards the projectile might fall roughly 3 to 4 inches below the line of sight; at 300 yards, on the order of 13 to 15 inches; and at 400 yards, perhaps 30 or more inches. Notice the fall roughly triples from the second to the third interval even though each step adds the same 100 yards, illustrating the squared relationship with time.
A Common Misconception
Many readers believe a projectile leaves the barrel rising under its own power before dropping. It does not climb on its own; it begins falling the instant it exits. Any apparent rise above the line of sight is only because the bore is angled upward relative to the sight line, so the descending gravity-driven arc still starts immediately at the muzzle.