1 - Open editor.

2 - Move to the airport's landing strip.

3 - Spawn the player. I used an Independent marksman.

4 - Spawn an OPFOR rifleman 350m away from the player. (It HAS to be 350m away, otherwise he'll either not see you at all (because you are too far) or kill you straight away (because you're too close))

5 - Shoot at him once just to get his attention.

6 - Go prone BEFORE he starts to shoot you.

7 - Notice how he takes quite a few shots to hit you. Pretty normal, considering he can barely see you with his red dot.

8 - Repeat all these steps, but instead of using a rifleman, spawn a sniper.
The sniper will spot you a lot faster, but will take roughly the same amount of shots to kill you. Not very realistic, considering he's go a huge scope on his accurate weapon. You can try it with an enemy marksman, he'l also miss quite a few shots.

1 My AI setting was on maximum, and so was the enemy's skill.

2 Even if the sniper has a spotter, it still takes quite a few shots to hit you. (Though not as many, but that's because the spotter will also try to shoot you, meaning they have doubled the firepower.)

3 Sometimes the AI get lucky and kill you very quickly, but other times they take almost an entire magazine.