Thermochemical analysis and field performance of small arms propellants from 1953 (30-06 M2 AP) and 2012 (M855A1) ammunition

When older stocks of ammunition are fielded for use, propellant degradation may be of concern. Degraded propellants may result in either increased or decreased chamber pressures, depending on formulation (thus deviating from expected performance), or in the worst-case scenario, auto-ignition. Data is sparse regarding propellants aged naturally in manufactured ammunition. Propellant harvested from 1953 U.S. military 30-06 M2 AP rifle cartridges and from 2012 U.S. military M855A1 rifle cartridgs was evaluated using thermochemical techniques and field testing. Thermochemical results were also compared with two 2022-era ball propellants (Winchester 748 and Hodgdon BL-C(2)). Thermal analysis demonstrated similar energy densities between the 1953, 2012, and ca. 2022-era propellants, with minor changes in activation energy, suggesting slightly decreased propellant thermal stability in the 1953 propellant. Chemical analysis supported this observation, with slightly decreased levels of stabilizer (still above accepted minimums) and increased levels of stabilizer byproducts in the 1953 propellant. For field testing, 0.223 Remington rifle cartridges were prepared for the 1953 and 2012 propellants utilizing the same match-grade components and a volume of the respective propellant to result in a muzzle velocity around 800 m/s. Accuracy characteristics and variation in projectile velocity were evaluated in a standardized competition course of fire. For each propellant, 20 rounds were shot from one bolt action rifle with a 1 in 8 inches twist, and 20 rounds were shot from another with a 1 in 7 inches twist. Results showed that the 1953-era propellant demonstrated comparable standard deviations in velocity and on-target precision to the 2012-era propellant, and both resulted in comparable standard deviations in velocity and on-target performance to a modern extruded commercial reloading propellant.