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Int J Legal Med. 2016 May;130(3):737-42. doi: 10.1007/s00414-015-1240-0. Epub 2015 Aug 4.

Modeling internal ballistics of gas combustion guns.

Author information

1
Department of Trauma and Orthopedic Surgery, University Medicine Greifswald, Sauerbruchstraße, 17475, Greifswald, Germany.
2
Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116, Braunschweig, Germany.
3
Department of Legal Medicine, University Medicine Greifswald, Kuhstraße 30, 17489, Greifswald, Germany.
4
Department of Trauma and Orthopedic Surgery, Unfallkrankenhaus Berlin (ukb), Warener Str. 7, 12683, Berlin, Germany.
5
Department of Trauma and Orthopedic Surgery, University Medicine Greifswald, Sauerbruchstraße, 17475, Greifswald, Germany. matthias.frank@uni-greifswald.de.
6
Department of Trauma and Orthopedic Surgery, Unfallkrankenhaus Berlin (ukb), Warener Str. 7, 12683, Berlin, Germany. matthias.frank@uni-greifswald.de.

Abstract

Potato guns are popular homemade guns which work on the principle of gas combustion. They are usually constructed for recreational rather than criminal purposes. Yet some serious injuries and fatalities due to these guns are reported. As information on the internal ballistics of homemade gas combustion-powered guns is scarce, it is the aim of this work to provide an experimental model of the internal ballistics of these devices and to investigate their basic physical parameters. A gas combustion gun was constructed with a steel tube as the main component. Gas/air mixtures of acetylene, hydrogen, and ethylene were used as propellants for discharging a 46-mm caliber test projectile. Gas pressure in the combustion chamber was captured with a piezoelectric pressure sensor. Projectile velocity was measured with a ballistic speed measurement system. The maximum gas pressure, the maximum rate of pressure rise, the time parameters of the pressure curve, and the velocity and path of the projectile through the barrel as a function of time were determined according to the pressure-time curve. The maximum gas pressure was measured to be between 1.4 bar (ethylene) and 4.5 bar (acetylene). The highest maximum rate of pressure rise was determined for hydrogen at (dp/dt)max = 607 bar/s. The muzzle energy was calculated to be between 67 J (ethylene) and 204 J (acetylene). To conclude, this work provides basic information on the internal ballistics of homemade gas combustion guns. The risk of injury to the operator or bystanders is high, because accidental explosions of the gun due to the high-pressure rise during combustion of the gas/air mixture may occur.

KEYWORDS:

Blunt ballistic impact; Blunt trauma; Gas combustion gun; Internal ballistics; Potato cannon; Potato gun; Spud gun

PMID:
26239103
DOI:
10.1007/s00414-015-1240-0
[Indexed for MEDLINE]

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