The Iron Sight is only available for the Ballista as the tenth and final attachment in multiplayer. This makes the weapon operate without its default scope, allowing for faster aiming time and better peripheral vision, but at the cost of a lower zoom level and the use of an attachment and one of the Pick 10 points.
The Iron Sight is available for the Pack-a-PunchedDSR 50 (Dead Specimen Reactor 5000) as one of the attachments cycled when upgraded multiple times, and for the Ballista by default in Origins (that are identical to its multiplayer counterpart). The Dead Specimen Reactor 5000's sights are quite open and less obstructive than the Ballista's. Overall, this attachment is rather effective in close quarters, more so than the scoped version. However, precise aim over long distances is more lacking, although given the ranges in the game mode are not very long, the Iron Sight can prove very useful in close to medium range.