Which of the following describes internal ballistics?

Internal ballistics refers to the study of the processes that occur within a firearm from the moment the trigger is pulled until the bullet exits the barrel. This includes various actions such as the ignition of the primer, the combustion of the propellant, and the resultant pressure that propels the bullet down the barrel. By understanding internal ballistics, one can analyze factors that affect the bullet's performance, accuracy, and safety within the firearm.

The correct choice highlights that internal ballistics encompasses all actions occurring before the bullet leaves the weapon, focusing on the events leading up to and including the bullet's exit from the barrel. This foundational knowledge is crucial for anyone interested in firearms, as it lays the groundwork for understanding how a bullet behaves once it has exited the barrel and throughout its trajectory.