If you are going into a total building level such as the Crespo Foundation, take along a shotgun or a submachine gun. The reticule does not shrink as much when you move with an assault rifle. You will move around a lot in buildings and room clearing. For places like an oil refinery, which has big indoor rooms and some outdoor areas, take an assault rifle that is compact to carry a punch but is still semi-maneuverable in rooms. In industrial indoor settings, take a sub that is good for big rooms and is still effective for small rooms. In total building settings, take along a shotgun. Its targeting reticule barely shrinks when you move.