Metal Gear Solid: Peace Walker/Extra Ops 005 - Marksmanship Challenge

With Puerto del Alba cleared, it is a good place for a training exercise.
 * Shoot all the targets in the staging area as quickly and accurately as you can.

Mission Prep
As with all missions for which Snake is not required, you should bring one of your low-ranking soldiers to pump up their GMP contribution. All the targets are in close quarters and are stationary, making it a good place to practice with the Mk.22. This may also be a good place to practice with the M16A1 if you wish. You don't need to bring anything else, or any kind of uniform.

Puerto del Alba
There are targets placed all over the staging area. You will move forward, taking out targets in front of you. Your route will be shaped like an S that ends at the base of the stairs up to the admin building.

You need to stop only to aim and you must only get headshots. Anything less, and you should restart the mission. Move, stop only to aim, and start moving immediately after you hear the shot break. If you start moving and shooting targets immediately, you can use the music to judge your timing; at the start of the song is a kind of arpeggio. When the music reaches this arpeggio again, you need to be within the final three targets at the northeast of the map. If you hear the arpeggio earlier than the final three targets, it is likely you took too long and need to restart.

Completion
Completing this mission with an S-Rank will yield 22 points, even if you went naked. There are no prizes for this mission, but it does yield progress for any R&D projects you have underway. If you've been following the walkthrough exactly, the M1911 and Stun Grenades will be complete. It's best to get the S-Rank on this one as early as possible.