The Department of Defense (DoD) has recognized heavy metal contamination as a critical environmental problem and assumed responsibility for reducing use of lead (Pb). In collaboration with SERDP and ESTCP, the Army has established the Green Bullet Program with the goal of completely eliminating lead in small caliber ammunition, including the percussion initiated primers. In lieu of the conventional lead styphnate and barium nitrate mixture, the small caliber lead free percussion primer relies on a novel and environmentally benign Metastable Intermolecular Composite (MIC) material. The Lead Free Electric Primer (LFEP) project will investigate the potential of scaling-up the small caliber percussion primer configuration to meet the needs of medium caliber (20mm) LFEPs. The 20mm weapons system is common to several aircraft in all three armed services and is part of the Navy's Phalanx Close-In Weapons System that provides ships with terminal defense.
The objective was to validate the substitution of environmentally friendly MIC materials for lead currently used in the manufacture of electrically initiated 20mm primers.
One difference between the existing and proposed primer is the need for the 20mm primer to be electrically conductive since it is initiated by a high voltage pulse from the weapon firing system. This increase in electrical conductivity was accomplished by the addition of "acetylene black" and some equivalent small particle carbon material to the MIC material. Beyond the substitution of the MIC materials, the LFEP utilized virtually the same components currently used in the manufacture of 20mm M52A3B1 electric primer. In addition to conducting laboratory tests on individual primers, the LFEP project fabricated 20mm rounds and fired them at the Navy's Ballistic Test Laboratory in China Lake, California. Key performance factors, such as muzzle velocity and action time, were measured during these tests.
This project demonstrated several key factors that support the use of MIC materials as a substitute for the heavy metal materials that are normally used in the production of electrically initiated primers. These factors include: (1) MIC materials can be made electrically conductive; (2) MIC can be safely handled and loaded into typical electric primer metal parts; (3) MIC-loaded primers can be initiated by voltage from ordinary aircraft gunfire; and (4) MIC-loaded primers can initiate the propellant bed of 20mm cartridges. This FY01 funded SEED project transitioned to a core FY03 New Start project (see WP-1331).
Major benefits derived through the substitution of MIC materials in medium caliber ammunition primers include reduced health and environmental risks to factory workers during primer mix manufacture and ammunition production processes, reduced risk to operational users who may be confined in spaces contaminated by residual weapons system gases containing lead, and cost savings from the avoidance of cleanup processes at both manufacturing and operational locations.