Big boy in Downtown area
In this mission, which is next to civil obedience 5, you need to collect 6 extra magazines, 5 scopes and 8 titanium bullets to destroy the robot in taking down big boy,
The items are mission specific and are dropped in downtown by military zombies. Since you will need at least 19 items you will need more then 25 crafted weapons (not all military zombies drop items).