title: Ballistics ordnance gelatine - How different concentrations, temperatures and curing times affect calibration results.
abstract: A study was undertaken to determine whether different concentrations of ordnance gelatine, water types, temperatures and curing times would have an effect on projectile penetration of a gelatine tissue surrogate. Both Federal Bureau of Investigation (FBI) and North Atlantic Treaty Organization (NATO) specified gelatines were compared against the FBI calibration standard. 10% w/w and 20% w/w concentrations of gelatine with Bloom numbers of 250 and 285 were prepared and cured at variable temperatures (3-20°C) for 21 hours-3 weeks. Each block was shot on four occasions on the same range using steel calibre 4.5 mm BBs fired from a Daisy(®) air rifle at the required standard velocity of 180 ± 4.5 m/s, to ascertain the mean penetration depth. The results showed no significant difference in mean penetration depth using the three different water types (p > 0.05). Temperature changes and curing times did affect penetration depth. At 10°C, mean penetration depth with 20% gelatine 285 Bloom for the two water types tested was 49.7 ± 1.5 mm after 21 h curing time, whereas the same formulation at 20°C using two different water types was 79.1 ± 2.1 mm after 100 h curing time (p < 0.001). Neither of the NATO 20% concentrations of gelatine at 10°C or a 20% concentration of 285 Bloom gelatine at 10°C met the same calibration standard as the FBI recommended 10% formulation at 4°C. A 20% concentration of 285 Bloom at 20°C met the same calibration/penetration criteria as a 10% concentration of 250 Bloom at 4 °C after 100 h of curing, therefore matching the FBI calibration standard for a soft tissue simulant for wound ballistics research. These results demonstrate significant variability in simulant properties. Failure to standardise ballistic simulants may invalidate experimental results.
authors.affiliation: The University of Adelaide, Discipline of Anatomy and Pathology, Frome Rd, Adelaide, South Australia, 5005, Australia. Electronic address: Nicholas.Maiden@adelaide.edu.au.
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Maiden
authors.affiliation: The University of Adelaide, Discipline of Anatomy and Pathology, Frome Rd, Adelaide, South Australia, 5005, Australia.
authors.forename: Wesley
authors.initials: W
authors.lastname: Fisk
authors.affiliation: Defence Science and Technology Organisation, PO Box 1500, Edinburgh, South Australia, 5111, Australia.
authors.forename: Christian
authors.initials: C
authors.lastname: Wachsberger
authors.affiliation: The University of Adelaide, Discipline of Anatomy and Pathology, Frome Rd, Adelaide, South Australia, 5005, Australia.
authors.forename: Roger W
authors.initials: RW
authors.lastname: Byard
mesh_terms: D044709:Forensic Ballistics / Q000295:instrumentation*; D005780:Gelatin; D013696:Temperature; D013997:Time Factors; D014867:Water
chemical_list: D014867:Water; D005780:Gelatin
keywords: Bloom; Calibration; FBI formulation; NATO formulation; Ordnance gelatine; Penetration depth