Visualization of the powder pocket and its influence on staining in firearm barrels in experimental contact shots

Abstract

The powder pocket or soot cavity is a morphologic characteristic of a close contact shot. In a research project concerning staining inside the barrel, the influence of the powder pocket on these traces was investigated.According to the 'triple contrast method', thin pads containing a mixture of acrylic paint, radiocontrast agent and blood were glued on plastic boxes which were coated with a 3-4-mm-thick silicone layer. The containers filled with 10 % ballistic gelatine, were stored for at least 60 h at 4 °C. Thirty-three contact shots were realized using different pistols and 22 lr, .32 auto, .38 special and 9-mm Luger with different barrel length using subsonic, non-deforming ammunition.The documentation comprised endoscopy, high speed video and computer tomography (CT) of the target models. Using image analysis, the ballooning of the silicone coat was studied (lateral view projection).High-speed video confirmed the actual comprehension of the behaviour of muzzle gases in contact shots. The powder cavity rises in about 1.5 to 2 ms, preceding the maximum of the temporary cavity, and the powder pocket's collapse takes 2.5 to 3 ms.The size of the silicone dome increased with decreasing barrel length. Comparing semi-automatic pistols of 4 in. barrel length in the calibres, .32 auto and 9-mm Luger, there were no significant differences of the powder pocket size. Material transport was observed, against and perpendicularly to the shooting direction. CT showed undermining and gas inclusions inside the powder pocket. A correlation between amount and pattern of the staining inside the barrel and the volume of the powder pocket was not observed.

Study of backspatter using high-speed video of experimental gunshots

“…7). The results reflected the increasing influence of muzzle gas [14], which is determined by the cartridge, the barrel length [23,24] and the gap between muzzle and target. The variable of the barrel length was eliminated by using only four inch barreled firearms in accordance with previously published articles [e.g.…”

“…All these approaches have particular advantages, but the common disadvantage was that the targets are not transparent and are dissimilar to human heads. The investigation of staining inside firearm barrels initiated using nontransparent silicone covered hemispheres [34], boxes [24] or polyethylene bottles [35]. With introduction of the "reference cube" with 12 cm edge lengths and a weight of 1.7 kg [10], a cheap transparent gelatin target model was available for reproducible ballistic experiments without ethical issues.…”

Efficiency of Determination of Elemental Composition of Metals and their Topography in Objects of Biological Origin Using Spectrometers

“…The results obtained by us make one deepen and supplement the previously known scientific and practical research. 3,9,12,14,17 When using X-ray fluorescence spectral analysis in cases of electric shock device applying, opens up opportunities not only to confirm the effect of electric shocker on the body, but also determine the conformity of the metal composition in the area of damage to the metal composition of the electrode, which may be important in establishing circumstances and conditions of injury. Thus, in our study, the constancy and conformity of the metal elemental composition in the areas of electric shock damage to the contact electrode metal was confirmed.…”

“…As practice shows, among many factors that characterize the features of gunshot wounds, detection of metals from bullets, shell casings, barrels of firearms formed during firing, and components of powder charge combustion, which are defined as "factors accompanying the shot" or "shot products " are provided sifficiently complete information. 3,12,14,17 It is essential to use the methods of elemental analysis and evaluation of the electrotag, which can act as an additional method of research that confirms the mechanism of damage, and even to some extent it indicates the electrode material that caused the damage. 7,8,13,18 Detection of chemical elements of metals in the composition of the shot products, electric tags and their identification is performed in the forensic laboratory by a set of methods and techniques known since the twentieth century.…”

Interpol review of forensic firearm examination 2016-2019

“…Although powder pocket volume decreases with increasing barrel length, no significant difference in powder pocket size was observed between .32 Auto and 9 mm Luger contact shots fired from barrels with the same length. No correlation between the amount and pattern of interior barrel staining and powder pocket volume was observed [ 171 ].…”