Distribution of tungsten on soil particles following firing of tungsten ammunition into various soil types.

Realistic training is the cornerstone for a viable military, and should be conducted while responsibly minimizing potential adverse impacts on human health and the natural environment. Metals and metal alloys are used in bullet manufacture to satisfy ballistic performance requirements as well as environmental concerns related to target practice and training. Soil types vary throughout the United States, and the variation in the soil provides a different impact for the bullets that are fired into them, due to their physical and chemical composition. Six different soil types characteristic of small-arms firing-range berm material located throughout the United States were fired into with lead and tungsten–nylon bullets, and were then analyzed to determine the bullet fragmentation characteristics in soils using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Scanning electron photomicrographs showed that typical lead–antimony alloy rounds produced discrete particulate-lead fragments following impact with the six backstop soils. Impacts of tungsten–nylon rounds produced smears or coatings of very fine tungsten–nylon on individual soil particles in the six soils and discrete tungsten particles in four of the six soils. The tungsten–nylon bullets generated a large number of small particles and smears with greater surface area per bullet impacted in the soil than the lead– antimony bullets, potentially increasing the dissolution and corrosion rate of the tungsten versus lead bullets in the berm material.