The objective of this project was to identify, characterize, evaluate, and test environmentally acceptable Metastable Intermolecular Composites (MIC) as a replacement for the hazardous lead, antimony, and barium compounds currently used in medium-caliber ammunition percussion primers.
Percussion primers are used to ignite ammunition propelling charges. To achieve their high degree of functional reliability, extremely sensitive primary explosive compositions are selected as the initiating material. Medium-caliber percussion primers typically consist of lead styphnate, barium nitrate, antimony sulfide, and other ingredients. Although highly effective, these heavy metal compounds have been identified as toxic pollutants. Disbursed in the immediate vicinity of military gunners or left to precipitate on training ranges and battlefields where they leach into the soil and groundwater, these heavy metal compound combustion byproducts present health hazards to soldiers, contaminate ranges, and require cleanup to mitigate future health risks.
Originally developed in the 1990s, the base MIC formulation of nano-sized particulate aluminum and molybdenum trioxide showed promise in small-caliber ammunition percussion primer applications. This project continued its development and extended its application to medium-caliber percussion primers. One issue with its use in medium-caliber applications is delayed action times under certain conditions. The first phase of this project was designed to better understand the reaction kinetics. Adding gas-generating additives to the base MIC formulation significantly improved performance. Further tailoring of this MIC+ composition in the laboratory established the proper charge load to achieve the functional reliability necessary to fire medium-caliber ammunition propelling charges within the required action times and at operating temperature extremes. Studies of proper mixing techniques to ensure a homogeneous composition and methods to mitigate the adverse effects of material aging were also conducted.
A successful demonstration of MIC percussion primers in medium-caliber ammunition was performed in April 2007. Provisional patent application number 60/917412 for the final MIC-based primer with booster ignition system was filed with the U.S. Patent and Trademark Office on 11 May 2007.
The main benefits of replacing conventional percussion primer compositions with MIC+ are the reduced risk to materiel operators and the cost savings from eliminating the need to clean up operational gunnery ranges contaminated with the fallout of lead, antimony, and barium compounds from the combustion byproducts of firing medium-caliber ammunition.