Metal Gear Solid: Peace Walker/Extra Ops 001 - Target Practice No Limit

How to unlock
Complete the mission Contact the Sandinista Comandante.

Extra Ops 001
There isn't much to this mission. Your weapons will have infinite ammo and you have all the time in the world to practice shooting. If you're not comfortable with the gunplay, you can either leave at the orange goal area or you can practice on infinitely-spawning paper targets. It is the same course fire you will be ranked on in [003] Target Practice: Score Attack, this will offer an opportunity to memorize it and practice your gunplay before you're tested for real.

More interesting than all that, however, is what's up on the second floor of the range. Climb upstairs and check out the catwalks. You'll find the T-shirt, a plain white tee that you can wear on missions. It doesn't affect defense, speed, or ammo capacity, but it does significantly reduce Camo Index in all environments compared to the OD green Jungle Fatigues. It does look comfy, though.

This mission is unranked and it does not add development progress to any R&D projects or count as time spent completing Outer Ops. You can always return to this mission for unlimited target practice to sharpen your gunplay.

It's a good idea to come back to this mission if you're not sure what to do to advance the plot.