Ballistic gelatine-what we see and what we get

Area of Science:

• Forensic Ballistics
• Material Science
• Biomechanical Engineering

Background:

• 10% gelatine is a standard medium for visualizing and estimating projectile energy transfer.
• Previous studies have relied on gelatine models to understand projectile-induced damage.
• The correlation between temporary cavity (TC) dynamics and actual tissue damage remains an area for refinement.

Purpose of the Study:

• To investigate the correlation between temporary cavity (TC) dimensions recorded by high-speed video (HSV) and the resulting crack patterns in gelatine.
• To evaluate the accuracy of 10% gelatine models in representing projectile energy transfer dynamics.
• To compare damage parameters for form-stable (FMJ) and deforming (HP) bullets across different calibres.

Main Methods:

• 36 shots with FMJ and 12 shots with HP bullets (.32 auto, .38 special, 9 mm Luger) into 10% gelatine cubes (12 cm edge length).
• High-speed video (HSV) recording of temporary cavity (TC) formation at 40,000 fps.
• Image analysis of scanned gelatine cross-sections to measure crack lengths, wound profiles, and TC heights along the bullet path.

Main Results:

• FMJ bullets created tubular TCs, consistent with their deceleration, while HP bullets produced pear-like TCs that did not accurately metricize deceleration.
• Destruction profiles (cracks) were convex for both bullet types and did not match bullet deceleration profiles.
• Maximum TC expansion in HSV did not coincide with maximum gelatine destruction (crack length); total energy transfer correlated with summed destruction parameters, but not per-centimeter energy deposition.

Conclusions:

• The 12 cm gelatine reference cube reflects overall energy transfer but does not precisely map energy deposition along the bullet path, especially for deforming projectiles.
• While total energy transfer shows correlation, specific destruction parameters (TC dimensions, crack lengths) have limitations in quantitatively representing ballistic energy transfer dynamics.
• Further research may be needed to refine gelatine models for more accurate ballistic simulations, particularly concerning the nuances of deforming versus non-deforming projectiles.