In a semi-automatic pistol, what component forces the rounds in the magazine upward?

The correct choice is the magazine spring, which plays a crucial role in the functioning of a semi-automatic pistol by pushing the rounds in the magazine upward. This mechanism is essential for the reliable feeding of cartridges into the chamber during cycling. When the slide moves back after firing a shot, the magazine spring compresses, and when the slide returns to its forward position, the spring applies pressure to the next round in the magazine, ensuring it is poised to be fed into the chamber for firing.

Understanding the function of the magazine spring is vital for grasping the semi-automatic feeding process. In contrast, components like the firing pin are responsible for striking the primer and igniting the round, while the slide release is involved in locking or releasing the slide rather than impacting magazine function. The action bar is not directly related to the magazine's operation; its role is more aligned with the movement of the slide in cycling through the chambering process. This knowledge is instrumental for anyone preparing for the Dallas Police Exam, as it highlights the importance of each component in ensuring the reliability and effectiveness of a semi-automatic pistol.