Which of the following is NOT an element of internal ballistics?

Internal ballistics refers to the processes that occur inside the firearm from the moment the cartridge is fired until the projectile exits the barrel. Key elements of internal ballistics include several critical phases of operation.

Propellant ignition is a crucial component as it initiates the combustion process that generates high-pressure gases within the cartridge, ultimately pushing the bullet forward. Bullet acceleration is another essential element, as it describes how the bullet gains speed while traveling through the barrel due to the expanding gases produced by the ignited propellant. The time until exit from the barrel indicates how long it takes for the bullet to travel the length of the barrel after ignition.

On the other hand, post-firing bullet drop is not considered an element of internal ballistics; rather, it falls under the realm of external ballistics, which deals with the bullet's trajectory and behavior after it exits the firearm. Therefore, this distinction clarifies why post-firing bullet drop is the correct answer, as it does not pertain to the internal processes occurring within the firearm at the moment of firing.