I have told the story before... guy I worked with was a Marine in Nam and used an M14with the early IR lash-up. One night he climbed a tree and was scanning the tree line across a paddy. Unfortunately, the bad guy evidently had a Dragunov with the scope that could see IR, so it was like shining a flasklight in the dark. Charlie didn't know the configuration because he fired directly at the light source instead of 6" lower to hit the shooter. The bullet knocked my friend out of the tree and destroyed the sight. He never used one again.