In external ballistics, the bullet travels in a curved path under the influence of gravity. Additionally, a spinning bullet may deviate laterally from the plane of fire due to the combined effect of spin and gravity. This lateral drift phenomenon is called:
- A Yaw
- B Precession
- C Derivation (drift) ✓
- D Deflection
Explanation
Derivation (also called drift) is the lateral deviation of a spinning bullet caused by the gyroscopic interaction of spin axis and the downward pull of gravity — the bullet's nose points progressively to one side (rightward for right-hand rifling). Yaw is the angular oscillation of the bullet's nose around the direction of travel. Precession (nutation) is a conical oscillation of the spin axis. Deflection refers to course alteration on striking an intermediate target. Understanding derivation is important when reconstructing long-range shots, where significant lateral displacement may occur.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
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Written and medically reviewed by the StethoPrep medical team.