What is "propellant combustion" or "powder burnt" or "z"?
Propellant combustion is the solid-to-gas conversion of the powder. The metric "z" defines the percentage of the burnt propellant when the projectile leaves the muzzle.
When optimizing a cartridge load through appropriate selection of components, combustion preferably ends before the projectile passes the muzzle. Achieving more than 95% of burnt propellant is considered to be a fair load. This improves energy utilization, ensures consistent results and somewhat influences the generation and appearance of muzzle flash.
- z = propellant combustion for standard barrel length
- z* = propellant combustion for short barrel length