Bull's EyeG 5

You should get this many just by completing the campaign, but you can also grind this out in a good spot if you don't want to bother. Play mission 6, and grab the sniper rifle when you come across it near the start. Keep playing through the mission until the first black loading screen. After this, go through the door and there's another sniper with more ammo on your right. Set up shop here and start taking out the following enemies; 1 across the courtyard to the right, one will jump into the fountain, and one on the far right underneath of you. 3 more enemies will then come out of the alleyway on the right. after that, an enemy will fire a rocket (I always reloaded here), then more enemies; 1 underneath of you, 2 across the courtyard near the tunnel, and one on the balcony. After that, 2 more enemies behind the truck on the left (one front, one back), then the last 2 on the far balcony. As soon as you kill those 2, reload your checkpoint and repeat. Try to be quick about your shots, or your squad will kill them first. I was getting 12 guys on average, and it only take a little over a minute per run.