The current firing drills just reward you for speed. It's a training for movement speed more than firing.
A vital aspect of real missions is left out: Spotting enemies, engaging them, especially from distance, and doing so accurately.
Therefore, I propose additional firing drills that have spotting and accurate firing as their main goal, not speed.
As an example: The player moves about on a rise near the town. In the town, targets pop up from time to time. The player is not informed about those targets, and has to find them himself, and shoot them. At the end of the course, the score is determined by the number of targets the player shot, not the time he took. An element of pressure can be introduced by popping up the targets for brief periods of time.