Use With Caution… (10)

Use the shotgun

You will come across the shotgun in mission eleven. After running into a locked door that needs to be accessed with a keycard, turn around, move forward a bit, and look to your left on the ground for a body. This body will have the keycard on it, along with the shotgun.

To use the shotgun, simply hold LT, then press RT to fire.

It is possible to obtain this achievement in Survivor mode prior to reaching mission eleven in the story. If you have the Crew Expendable DLC you are able to use Dallas, Ellen Ripley, and Parker in Survivor mode.

Dallas automatically has a shotgun in his inventory.