The relationship between pellet size and shotgun dispersion patterns.

Area of Science:

• Forensic Science
• Ballistics
• Ammunition Analysis

Background:

• Determining muzzle-to-target distance in shotgun incidents relies on comparing crime scene dispersion patterns with test shots.
• Using identical ammunition for test shots is ideal but often unfeasible, necessitating the use of alternative cartridges with different pellet sizes.

Purpose of the Study:

• To investigate the relationship between shotgun pellet size and the resulting dispersion pattern size.
• To evaluate the impact of using different pellet sizes on dispersion patterns when other ammunition components remain constant.

Main Methods:

• Conducted test firings using identical shotgun cartridges (cases, powder, wads) but varied pellet sizes (below size B) for both lead and steel shot.
• Measured and compared dispersion pattern sizes at a fixed distance (5 meters) from the muzzle.

Main Results:

• Shotgun dispersion patterns increase as pellet size decreases for both lead and steel shot, provided other factors are equal.
• Pattern size was approximately 1.7 times larger with #9 lead shot compared to #0 lead shot.
• Pattern size was approximately 1.4 times larger with #9 steel shot compared to #1 steel shot.

Conclusions:

• The study confirms that pellet size is a critical factor influencing shotgun dispersion.
• Findings support the use of alternative ammunition with slightly different pellet sizes for test shots in forensic analysis, with careful consideration of the observed effects.
• The data provides a quantitative basis for adjusting muzzle-to-target distance estimations when substituting pellet sizes.