Currently, all small-caliber tracer and incendiary ammunition is produced at the Lake City Army Ammunition Plant (LCAAP) in Independence, Missouri. So that soldiers or marines can select the correct ammunition while in combat or training, the ammunition is made identifiable by applying low volatile organic compound (VOC) paint to the projectile tip. The conventional spray- or dip-paint application processes are sensitive to several atmospheric factors, are inefficient and wasteful, release toxic solvents, and cause environmental and occupational health and safety hazards. As a substitute for traditional paint application processes, this project investigated a powder coating technology at the Concurrent Technologies Corporation (CTC) test facility in Johnstown, Pennsylvania.
Powder coatings are composed of finely ground plastic particles, which consist of resins, pigments, fillers, binders and hardeners, but no solvents. When exposed to heat, the plastic particles melt or react and flow to form a continuous film of high durability and chemical resistance. No toxic gases are emitted when powder coatings are applied or cured. Powder coatings are typically applied using electrostatic spray equipment and cured in an oven. They can be either thermoplastic or thermoset.
At the CTC test facility, 7.62-millimeter (mm) tracer projectiles were loaded on a test jig, powder-coated with an epoxy-based thermoset paint using a manual electrostatic spray gun, and then cured in an oven. By performing standard Lot Acceptance Tests, which included coating adhesion and finish quality, and quick and easy visual identification of bullets, these projectiles were compared with similar projectiles that had been coated in a conventional painting process at LCAAP. The powder coating was resilient and represented an improvement over the conventional process. Both samples of projectiles were subsequently loaded into cartridges at LAAP, and ballistics tests were performed on the LAAP test range. The accuracy, velocity and trace performance of each were indistinguishable.
Powder coatings can be stored indefinitely, have a lower curing time, and are more easily removed from spray equipment as compared to conventional liquid paints. The use of hazardous solvents in the paint formulation would be eliminated, and the occupational health of workers would improve. However, implementation on the 7.62-mm cartridge line alone at LCAAP would not be economically justifiable due to the currently low throughput rate. The payback on the estimated $40,000 cost for the required facility modifications would be 4-5 years unless the technology was also implemented on other types of ammunition. Powder coating is a versatile technology that is applicable to several calibers of ammunition at LCAAP, and implementation for a wide range of ammunition may be appropriate. Material (i.e., projectile) handling methods however would have to be developed, and the safety issues concerning the heat sources used to cure the paints in the proximity of live ammunition would have to be addressed.