Topical Issues of Forensic Research of Firearms with Oval-Screw Drilling of the Bore “Lancaster” and Its Traces on the Bullets

Abstract

The article discusses the issues of developing the legal, scientific, and methodological foundations of the forensic investigation of firearms with oval-screw drilling of the Lancaster barrel bore. The author makes some proposals on how to bring the norms of the regulatory and technical regulations in the field of arms and ammunition trafficking in line with the modern concepts of rifled firearms. The mechanism of formation of traces of the barrel bore on the fired bullets is revealed. The author notes that the drilling of the Lancaster barrel bore determines the appearance of traces from its oval-screw profile in the form of two areas of abrasion along the small axis of the oval (traces of rifling lands) and two areas of less intense abrasion along the large axis of the oval (traces of rifling) on the bullets. The traces of the rifling lands and the traces of the rifling are fused with each other, and have a small angle of inclination (about 3° ).The dependence of the display of traces of the barrel bore with the Lancaster drill on the fired bullets on the design of the bullets of the cal cartridges has been established. .366 TCM, 9.6x53 Lancaster. When using cartridges with FMJ shell bullets and SP “KION” semi-shell bullets, the traces of the barrel bore are displayed sufficiently well, which, in general, makes it possible to identify the weapon. Firing cartridges with an all-metal bullet made of zinc alloy “ECO” dramatically reduces the display of traces of the barrel bore on the fired bullets and complicates the firearms identification. The author proposes to ban shooting cartridges with lead bullets with a polymer antifriction shell “DERI” in firearms with a Lancaster channel drill, since when firing, the traces of the barrel bore on the fired bullet are not displayed. This contradicts the legislator’s requirement for civilian models of firearms on mandatory formation of traces suitable for identifying weapons on fired bullets.