Possible influences on bullet trajectory deflection in ballistic gelatine

•A model to study bullet deflection due to gelatine perforation is proposed.•Deflection angles seem to be constant for an established gelatine depth.•No significant influence from previous shots or gelatine sides has been observed.

The influence of the distance to the top and bottom of a gelatine block and to bullet tracks from previously fired shots on a bullet's trajectory, when passing through ballistic gelatine, was studied. No significant difference in deflection was found when trajectories of 9 mm Luger bullets, fired at a 3.5 cm distance to the top and bottom of a gelatine block and to bullet tracks from previously fired shots, were compared to trajectories of bullets fired 7 cm or more away from any of the aforementioned aspects. A surprisingly consistent 6.5° absolute deflection angle was found when these bullets passed through 22.5 to 23.5 cm of ballistic gelatine. The projection angle, determined by the direction of the deflection, appeared to be random. The consistent absolute angle, in combination with the random projection angle, resulted in a cone-like deflection pattern.