Gravity Drop
Definition
The vertical distance a bullet falls below the bore axis at a given horizontal range, accumulating continuously from the instant of muzzle exit under the acceleration of gravity (9.81 m/s^2).
- Physical quantity
- Vertical fall below bore axis at given range
- Acceleration used
- 9.81 m/s squared
- Starts from
- Instant of muzzle exit
- Related concepts
- Zero range, point-blank range
Common questions
Why does a bullet still drop even though the barrel is aimed slightly upward?+
The sights are angled up relative to the bore so the bullet's trajectory crosses the line of sight at the zero range, but gravity acts on the bullet continuously from the moment it leaves the muzzle regardless of that angle, so the bullet is always falling away from the straight bore-axis line even while it is still rising relative to the line of sight.
Does bullet velocity change how fast gravity drop accumulates?+
No, a faster bullet reaches a given range sooner and so has less time to drop, but the rate of fall itself is governed only by gravitational acceleration, not by the bullet's speed, which is why gravity drop calculations are essentially a time-of-flight problem rather than a ballistic-coefficient problem.
Related terms
- Ballistic Solver
- Software (JBM Ballistics, Strelok Pro, Hornady 4DOF, AB Quantum) that computes trajectory accounting for drag, BC, muzzle velocity, and atmospheric conditions. Supplementary...
- Battle-Sight Zero (BZO)
- The zero range selected by a military or paramilitary organisation as the standard setting for field use. US Army M4: 300 m....
- Bore Axis
- The centreline of the barrel through which the bullet travels. The starting reference line for measuring gravity drop and the elevation difference...
- Near-Zero Crossing
- The shorter of the two distances at which the bullet's trajectory intersects the line of sight. For a rifle zeroed at 300...
- Point-Blank Range (PBR)
- The maximum distance at which the bullet stays within the vital-zone radius above or below the line of aim without the shooter...
- Trajectory Rod
- A rigid fibreglass or aluminium rod inserted through a bullet wound channel and aligned with the channel geometry to define the bullet's...
- Vital Zone
- The defined target area used to compute point-blank range. For human thorax: typically 20 cm diameter (10 cm radius) centred on the...
- Zero Range
- The horizontal distance at which the bullet's trajectory crosses the line of sight. At this range, the point of aim and point...