Effect of the Initial Temperature on the Characteristics of the Shot with a Block Charge

Abstract

The effect of the initial temperature on the characteristics of the shot is studied for high-density block charges prepared by pressing powder grains coated with a polymer film. The experiments were carried out on laboratory barrel setups of caliber 7.62 and 14.5 mm with recording the muzzle velocity and pressure. Two shot schemes are considered: a classical scheme with the block charge placed in the chamber, and a hybrid scheme, with the block charge attached to the projectile, burning as it travels along the barrel. The effect observed at various initial temperatures of the block charge is compared with similar data for a standard poured-powder charge, for which the temperature gradient within ±50°C is 2.1−2.5% per 10°C. The experiments showed that, at positive temperatures, the temperature gradient for block propellant charges is appreciably smaller, 0.9−1.2% for the traditional shot scheme and 0.8% for the hybrid scheme. At negative temperatures of the block propellant charges, the characteristics of the shot decline significantly, which, however, can be restored to the temperature gradient typical of the standard shot by boosting the igniter.