Kane & Lynch: Dead Men

This Achievement unlocks after 30 cumulative kills with the shotgun. They can be obtained on any difficulty level, across any chapters that you play. Close quarters indoor fights are better suited for the shotgun than open space long-range combat, so choose your weapon accordingly.

Once you get to the car on the Trial level, you can swap guns with Lynch as he seems to always get the shotgun. Push down on both the LS and RS at the same time to exchange weapons. As Kane, every new level means you lose the shotgun so just switch again with Lynch.

The shotgun has poor range but has a lot of power in tight. You should get this fairly easily.