Go on 'forge' with 2 people, turn into the robot and get a shotgun.

The person and the robot have to pick up the shotgun at the same time.

You do not need to push any other button except the right bumper like you normally would, and the robot would normally push 'A' (the green button).

You can not reuse the same shotgun.

When you have it, the person's arm will be bent back, but the shotgun will still shoot.