弾丸の変形に伴う弾径と腔旋痕角の変化（第２報)—パルティックの場合

抄録

  Some .38 caliber revolvers smuggled into Japan are homemade guns called Paltik which were made in Cebu Island, the Philippines. Bullets fired from a Paltik have the following general characteristics;
(1) Rifling mark is rough and unclear because of the inferior processing of the finished rifling bore.
(2) Bullet is elongated because the bore diameter is usually smaller than an authentic gun.
  But some Paltik bullets nowadays have a neat rifling mark. The diameter in the base of the lead bullet may have been changed thus having the rifling mark deformation become indistinct. In such cases, it becomes more difficult to distinguish fired bullets between those fired from a Paltik and an authentic gun.
  In a former report, the maximun rate of contraction in the base of lead bullets and reduction of the angle of twist on the rifling mark fired from an authentic gun was indicated. But because the shape of bullets fired from a Paltik whose bore diameter is smaller, the deformation characteristic becomes long and narrow, so it is necessary to discriminate the characteristics of deformation on bullets fired from a Paltik and from an authentic gun.
  In this study, .38 Special lead bullets were shot into thick steel plate in a right angle from a Paltik whose bore diameter is 8.45 mm (diameter of fired bullet is 8.58 mm). The following results were obtained and it was concluded that there were few differences in characteristics of deformed bullets between a Paltik and an authentic gun.
A) The diameter in the base of bullets was contracted up to 0.59 mm (8.58 mm → 7.99 m, 6.9% smaller) in a Paltik. On the other hand, it was 0.6 0mm (9.00 mm → 8.40 m, 6.7% smaller) in an authentic gun.
B) The angle of twist of rifling mark reduced 0.75° (6.90° → 6.15°, 11% smaller) in a Paltik. On the other hand, it was 0.79° (3.30° → 2.51°, 24% smaller) in an authentic gun.