Modeling the influence of yaw rate on the tumble depth for small caliber bullets

Authors:

  • Thomas Öst

Publish date: 2016-12-12

Report number: FOI-R--4332--SE

Pages: 22

Written in: Swedish

Keywords:

  • Small caliber
  • finite element modeling
  • ballistic gelatin
  • tumble depth

Abstract

In ballistic experiments using small caliber bullets, it is always important to obtain repeatable results and to know the ballistic properties of the bullet at impact such as speed and angle of attack. These properties are therefore often measured during experiments as they have a large influence on the behavior in e.g. soft targets. Other properties, such as spin or pitch rate, however, are much more difficult to measure directly in the experiments and are sometimes instead calculated based on e.g. known properties of the barrel and muzzle velocity. As particularly properties such as the pitch rate is very difficult to assess, numerical methods is a valuable tool to determine their effect as exact quantities for the bullet properties are determined a priori. This report shows how the pitch rate influences the depth where a bullet starts to tumble while varying the angle of attack in a soft target using finite element modelling. The results show that under normal conditions in ballistic experiments with a direct hit, the pitch rate is quite small and only has a minor effect on the reduction in the depth where tumbling start. For larger pitch rates, e.g. that are obtained in ricochet experiments, the effect on the reduction in the depth where tumbling start is much larger, despite a fairly low angle of attack.