Iron sight

Background


The iron sight is a open, unmagnified system used to assist the aiming of typically firearms. Several weapons, such as the M7 Caseless Submachine Gun and M90 Close Assault Weapon System, utilizes an iron sight, however other UNSC weapons, e.g. the MA5B and MA5C Assault Rifle's, the Machine Gun Turret, and some M6 handguns do not seem to use them, but it has been speculated that it is due to the fact that Marines and Spartans who operate these weapons have HUDs that assist them, negating the need for iron sights. This is probably a reason why personnel who don't have HUDs can't and don't use these weapons.

Operation and Adjustment
Iron sights work by providing and advocating a horizontal and vertical reference point that allow the shooter to actually align the gun parallel to the shooter's line of sight and crosshair. Once the sights are precise with each other, they are placed in correct relation to the target. This places the gun at a precise angle to the line of sight to the target. With appropriate compensation for range to the target, parallax between the iron sights and the gun's bore, and the trajectory of the projectile, a shot fired will hit the target.

Since the eye is only capable of focusing on one plane, and the rear sight, front sight, and target are all in separate planes, only one of those three planes can be in focus at one time. Which plane is in focus depends on the type of sight, and one of the challenges to a shooter is to keep the focus on the correct plane to allow for best sight alignment. A tiny error in sight alignment can be multiplied hundreds or thousands of times by the time the projectile reaches the target.

Examples of Weapons Featuring the Iron Sights

 * M7 Caseless SMG
 * M7S Caseless SMG
 * M90 Shotgun Series
 * DTM/Law Enforcement (Possibly)
 * M6C Magnum

Trivia

 * Interestingly enough, as the standard service rifle for the UNSC forces, the MA5 series (except for the MA5K) of firearms do not sport any form of sights or optics. It may be replaced with the targeting reticule in a Spartan's HUD or a UNSC Marine's eyepiece, but Marines in Halo 3 do not have any eyepieces, thus rendering the aiming of the weapon close to impossible.
 * A possible explanation for the above is either that the UNSC Marine's Neural Interface brings the HUD on their retina or that the MA5B and MA5C have hidden Iron sights that can pop up.