Metal Gear Solid: Peace Walker/Extra Ops 006 - Marksmanship Challenge

The boathouse on the Río del Jade has been cleared of enemy presence and presents a great opportunity for marksmanship training at mid-to-long distances.
 * Complete the marksmanship training course at the boathouse on the Río del Jade.

Mission Prep
This mission can be completed with any weapon since all weapons are hitscan and have no bullet drop. Go ahead and equip the Mk.22 so you can get some experience and practice with it. Consider bringing a longer-range weapon such as the M16A1 to supplement the Mk.22, but ignore Miller's instructions to bring a sniper rifle. The sniper rifle's firing rate and magazine capacity are too small to meet this mission's steep S-Rank requirements.

Río del Jade
Targets are stationary but scattered at various heights around your starting point. They're all facing toward your location, so there's no reason to move. It would cost you your S-Rank anyway.

The second you can start, walk forward to the edge of the house and crouch with to bolster your accuracy. If you fall off the edge, you failed and need to restart. The requirements are that taxing. Angle the camera to your right.

You need to hit all targets within 1 minute and 16 seconds and you need all of them to be headshots in order to get an S-Rank. The dry runs will be taxing but will make you a better shot in the end. Shoot the targets in the order annotated on the map above. You can hit all of them with the Mk.22, but you could consider using the M16A1 to hit the more distant targets, but you should waste no time swapping weapons.

To get the most out of this mission, every single shot needs to be a headshot. Miss even one, and you need to start over. Do some dry runs so you can minimize your mission time; once you hit them all, restart. When you feel like you can hit all targets in the head under 1:16, go ahead and finish the mission.

Once all targets are hit, waste no time getting down to the ground and get to the Recovery Point in front of the mounted machine gun.

Completion
There are no rewards for this mission. You'll get 22 points added to Heroism for completing this mission with an S-Rank.

If you've been following this walkthrough precisely, the ★1 M10 and ★2 Fulton Recovery System should be complete, and the soldiers who went to the brig from the mission Armored Vehicle Battle: LAV-Type G will start trickling out of the Brig and joining MSF. With the exception the C-ranked or high D-ranked Mechanics, all those soldiers should go to the Combat Unit.