Zero Range
Definition
The horizontal distance at which the bullet's trajectory crosses the line of sight. At this range, the point of aim and point of impact coincide (accounting for sight height above bore).
- Defined as
- Range where trajectory crosses line of sight
- Effect at zero range
- Point of aim equals point of impact
- Depends on
- Sight height above the bore
- Number of crossings
- Trajectory crosses the sight line twice
Common questions
Why does a bullet's trajectory cross the line of sight more than once?+
Because the sight sits above the bore axis, the bullet starts below the line of sight at the muzzle, rises to cross it at the near zero, continues briefly above it, then falls back to cross it again at the set zero range, after which it drops increasingly below the line of sight as range increases.
How is zero range relevant to reconstructing a shooting incident?+
If the firearm's zero range is known or can be estimated, an examiner can calculate how far the actual point of impact would have diverged from the shooter's point of aim at the incident distance, which feeds into trajectory and shooter-position reconstruction.
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...
- Gravity Drop
- The vertical distance a bullet falls below the bore axis at a given horizontal range, accumulating continuously from the instant of muzzle...
- 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...