Kane & Lynch 2: Dog Days

Load up chapter 2 "The Details" on easy difficulty. This chapter starts you out with a shotgun. This is the chapter where you are ambushed on the freeway.

It's pretty straightforward. However, note, there is no timelimit for this achievement. So take your time and use cover; make sure your shots are lined up correctly. Even on easy mode there is about 15 guys all shooting at you at once so it can get frustrating if you're impatient.

If you don't get it at the start of the chapter just press start and restart the chapter. It's best to do this right at the beginning.

Heres a quick guide on how to get this achievement

Blood, Sweat and Tears
Easy

Start the mission and try to get a shotgun as early on as you can, keep this shotgun all the way through. Play up until the point where you have to destroy the van, once you have destroyed the van the Police will come into the building. They basically set themselves up for the achievement. Equip your shotgun and kick the door down, from now until near the end of the level there will be 6 police officers, storm them and shoot each one once, when you reach the doorway at the end you should have the achievement.