What does External Ballistics refer to in firearms?

External Ballistics specifically refers to the behavior of a bullet after it exits the barrel of a firearm. This includes understanding the bullet's trajectory, velocity, and how various factors such as wind resistance, gravity, and atmospheric conditions influence its flight path until it reaches the target. This encompasses a number of concepts such as ballistic coefficient, stability, and range.

Understanding external ballistics is crucial for shooters and marksmen as it impacts accuracy and effectiveness, helping them to account for environmental variables that can affect their shots. The other options address different aspects of firearms and ammunition but do not pertain to the bullet's behavior in flight after exiting the barrel. For instance, the design of the firearm barrel relates more to internal ballistics, the preparation of ammunition deals with loading and assembly but not how the bullet behaves after firing, and cleaning the firearm is about maintenance and does not influence ballistics at all.