title: Energy-dependent expansion of .177 caliber hollow-point air gun projectiles.
abstract: Amongst hundreds of different projectiles for air guns available on the market, hollow-point air gun pellets are of special interest. These pellets are characterized by a tip or a hollowed-out shape in their tip which, when fired, makes the projectiles expand to an increased diameter upon entering the target medium. This results in an increase in release of energy which, in turn, has the potential to cause more serious injuries than non-hollow-point projectiles. To the best of the authors' knowledge, reliable data on the terminal ballistic features of hollow-point air gun projectiles compared to standard diabolo pellets have not yet been published in the forensic literature. The terminal ballistic performance (energy-dependent expansion and penetration) of four different types of .177 caliber hollow-point pellets discharged at kinetic energy levels from approximately 3 J up to 30 J into water, ordnance gelatin, and ordnance gelatin covered with natural chamois as a skin simulant was the subject of this investigation. Energy-dependent expansion of the tested hollow-point pellets was observed after being shot into all investigated target media. While some hollow-point pellets require a minimum kinetic energy of approximately 10 J for sufficient expansion, there are also hollow-point pellets which expand at kinetic energy levels of less than 5 J. The ratio of expansion (RE, calculated by the cross-sectional area (A) after impact divided by the cross-sectional area (A0) of the undeformed pellet) of hollow-point air gun pellets reached values up of to 2.2. The extent of expansion relates to the kinetic energy of the projectile with a peak for pellet expansion at the 15 to 20 J range. To conclude, this work demonstrates that the hollow-point principle, i.e., the design-related enlargement of the projectiles' frontal area upon impact into a medium, does work in air guns as claimed by the manufacturers.
authors.affiliation: Landeskriminalamt Brandenburg (LKA BB), Forensic Institute, Tramper Chaussee 1, 16225, Eberswalde, Germany.
authors.forename: Ronald
authors.initials: R
authors.lastname: Werner
authors.affiliation: Landeskriminalamt Brandenburg (LKA BB), Forensic Institute, Tramper Chaussee 1, 16225, Eberswalde, Germany.
authors.forename: Benno
authors.initials: B
authors.lastname: Schultz
authors.affiliation: Department of Legal Medicine, University Medicine Greifswald, Kuhstraße 30, 17489, Greifswald, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Bockholdt
authors.affiliation: Department of Trauma and Orthopedic Surgery, University Medicine Greifswald, Sauerbruchstraße, 17475, Greifswald, Germany.|Department of Trauma and Orthopedic Surgery, Unfallkrankenhaus Berlin (ukb), Warener Str. 7, 12683, Berlin, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Ekkernkamp
authors.affiliation: Department of Trauma and Orthopedic Surgery, University Medicine Greifswald, Sauerbruchstraße, 17475, Greifswald, Germany. matthias.frank@uni-greifswald.de.|Department of Trauma and Orthopedic Surgery, Unfallkrankenhaus Berlin (ukb), Warener Str. 7, 12683, Berlin, Germany. matthias.frank@uni-greifswald.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Frank
mesh_terms: D000388:Air; D005389:Firearms; D044709:Forensic Ballistics / Q000379:methods*; D006801:Humans; D007700:Kinetics; D015233:Models, Statistical
keywords: Air gun pellet; Ballistics; Deformation bullet; Hollow-point bullet; Kinetic energy; Temporary cavity