I've got a few tips for getting the Killing Time badge:
For the sniping: dont save the hardest targets for last. when you have a very strong wind speed, aim for an easy target. When there is a weak wind, aim for the harder ones. Just practice a few times!
Pistol Challenge: Just do this challenge a few times, you'll get the hang of it.
Hostile Area: There is a very handy trick to do this. You should shoot only 1 enemy (100% accuracy!) and then let them kill you. It gives you a score of 10100
Gun Running: Use the auto-shotgun to shoot the targets.
Long Range: I dont really have a tip for this one
Good luck getting the badge! + for more people to read!