Bullet Trajectory

How the bullet trajectory works

Two points on a bullet's path define a line, and that line can be measured. In practice the points come from two perforations in a single object, from an entry and a corresponding exit in a room, or from a trajectory rod placed through one perforation and aligned with a defect beyond it.

The vertical angle gives elevation or declination and the azimuth gives left or right deviation from the reference axis. Projecting the line backwards to a chosen distance gives a muzzle height at that distance, which is what narrows down whether a shot came from standing, seated, or elevated position.

Frequently asked questions

How do you calculate a bullet trajectory angle?

Take the vertical difference between two points on the path and divide it by the horizontal distance between them, then take the arctangent. The same calculation on the lateral offset gives the azimuth.

What is the difference between angle of incidence and azimuth?

Angle of incidence is the vertical angle at which the bullet met the surface. Azimuth is the horizontal angle, measured left or right of the reference axis. Both are needed to place a shooter in three dimensions.

Does this account for bullet drop?

No. It models a straight line, which is a fair approximation over the short distances typical of an indoor scene. Over longer ranges gravity drop and drift make the real path a curve, so the straight-line angle understates the elevation.

Can a trajectory prove where the shooter stood?

It defines a probable line, not a point. Perforation shape, intermediate targets, ricochet, and deflection inside material all introduce uncertainty, so a reconstruction gives a zone rather than a position.

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