Frangible ammunition is adaptable to both rifles (top) and hand guns (bottom)  
 

Compressed powders 9mm W-Sn (left) 9mm W-Zn (right)

The firing of small arms ammunition for training, sport, law enforcement, and military purposes is a major source of environmental pollution. The lead from shot and bullets is a significant environmental and health problem at numerous public, private, and government-operated shooting ranges. Many sites are contaminated with hundreds of tons of lead, the result of years of shooting and target practice. Lead is tainting grounds and water, and is being ingested by wildlife, and has thus become a serious threat to the health and safety of human and animal populations. Indoor ranges pose other serious concerns such as increased lead exposure to the shooter due to the enclosed space and the subsequent need for high capacity ventilation and air filtration systems. Handling of ammunition and contaminated weapons can also produce elevated lead levels in the blood by absorption through the skin.

A non-toxic, all-metal replacement for lead in bullets has been developed at the Department of Energy's Oak Ridge National Laboratory (ORNL). Powder metallurgy techniques have been used to produce metal-matrix composite simulants that have properties very similar to those of lead. Bullets are fabricated from mixtures of powdered metals that are simply pressed at room temperature to produce a high-density material. No heat treating or sintering is necessary to
achieve densities and mechanical properties that mimic those of lead and its alloys. Mechanical interlocking and "cold welding" bond the metals together, and can be varied to control the properties of the lead replacement. Bullets can be pressed directly to shape, or "slugs" can be produced that can be swaged into projectiles, with or without jacketing.

Non-lead bullets fabricated employing powder metallurgy simulants have proven to be one-to-one replacements for their lead analogs. Ammunition has been assembled using non-lead bullets and propellant charges matching currently available products. Velocity and chamber pressures were found to be similar to those for the lead-containing projectiles. Accuracy has also been examined and, in many cases, is improved through the use of the non-lead material.

The use of powder metallurgy provides greater flexibility in controlling bullets' properties. Processing conditions, composition, and powder particle size can be used to alter density and impact behavior. The latter is of significant importance in situations where penetration, ricochet, and collateral damage are concerns. The properties of non-lead 
materials can be controlled so that a bullet fragments into small particles upon impacting a hard target, but remains intact when engaging a soft target. A "frangible" bullet is desirable for close-quarters training, and extends response team capabilities in specialized environments. In addition, the density of the material can be varied over a broad range, allowing for new designs and improvements in ballistic performance.

Significant achievements have been realized in this project. Numerous patent applications have been filed, allowing the technology to be marketed for technology transfer. The project continues to progress, and has been reviewed by many organizations with enthusiasm. ORNL is a member of the Interagency Working Group for Non-Toxic Small Arms 
Ammunition, also known as the "Green Bullet" team. At this time, non-lead bullet material composed of tin and tungsten is the leading candidate for use in military ammunition. Tens of  thousands of rounds have been tested by the military with exceptional results. A procurement of 1 million rounds of ammunition is planned for 1999, with increased numbers in following years.