Don't hold your breath Achievement

Note: If playing in co-op, this does not unlock for both players, so create a save beforehand.

This is unlocked in Mission 8, ‘Rubble and Ruin’. At the end of the mission, after running out of the U-boat pen, you realize that your sabotage did not work. Follow the yellow marker and climb up the ladder into a radio room. Peering out the vantage point overlooking the pen, the giant door will open, giving you a clear shot at the fuel tanks.

You must take this 275+ meter shot without pressing or to empty your lungs. Crouching or going prone for a couple of seconds before looking out the window and taking the shot will lower your heart rate faster to steady your shot, and having a rifle with at least an 8x magnification and playing on ‘Civilian’ difficulty (so there’s no bullet drop or wind) will help immensely.

Aim through your rifle scope at the dark grey control panel on center fuel tank, and once it’s in your sights, take the shot. If your shot is accurate, a cutscene will play of the base being destroyed and the achievement will unlock.