COMPARING LEAD-BASED (CCI 41) AND LEAD-FREE (RUAG SINTOX) PRIMER PERFORMANCE IN 5.56MM NATO

Abstract

Previous work identified significant problems with lead-free primers reliably igniting propellant charges in 5.56 mm NATO and other cartridges. These problems include high incidence of misfires, increased barrel friction, and long ignition delays. To date, no lead-free primer has been identified which meets NATO ignition requirements and works with a range of propellant types after prolonged exposure to humidity. Ruag SINTOX primers are marketed to meet NATO specifications, but it was unclear how they would respond to exposure to humidity commonly encountered in real-world environments. This paper reports results of performance and ignition delay testing of lead-free Ruag SINTOX and lead-based CCI 41 primers after exposure to typical indoor ambient humidity (40-60% relative humidity) and 100% relative humidity for 8 months (both at ambient temperature). Tests were performed using four propellant types: Alliant Blue Dot (a flake powder), Hodgdon H4895 (a cylinder powder), St. Mark's SMP842 (a flash suppressed ball powder), and the Ruag ball powder that the SINTOX primers are paired with in Ruag's lead-free ammunition. The Ruag lead-free SINTOX primer performed comparably to the CCI 41 lead-based primer in all tests and met the NATO specification for ignition delay (< 4 ms), even after 8 months of storage exposed directly to 100% humidity.