Iron sight

Operation


The iron sight is a open, unmagnified system used to assist the aiming of a variety of devices, usually those intended to launch projectiles, typically firearms. Several weapons, such as the M7 and M90, utilizes an iron sight, however other UNSC weapons, e.g. the Assault Rifle, the Machine Gun Turret, and some M6 handguns do not seem to use them for reasons unknown.

How it works
Iron sights work by providing horizontal and vertical reference points that allow the shooter to align the gun parallel to the shooter's line of sight. Once the sights are aligned 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. 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; for example, with an Olympic-class air rifle shooter trying to hit the 10 ring, which is 10 mm in diameter, with a 4.5 mm diameter pellet at 10 meters, an error of 0.2 mm in sight alignment can mean a miss. At 1000 meters, that same 0.2 mm misalignment would be magnified 1500 times, giving an error of over 300 mm. (Calculations assume a 660 mm sight radius)

Sights for shotguns used for shooting small, moving targets work quite differently. The rear sight is completely discarded, and the rear reference point is provided by the correct and consistent positioning of the shooter's head. A brightly colored (generally brass or silver colored, white, or a fluorescent shade) round bead is placed at the end of the barrel. Often this bead will be placed along a raised, flat rib, which is usually ventilated to keep it cool and reduce mirage effects from a hot barrel. Rather than being aimed like a rifle or handgun, the shotgun is pointed — the focus is always on the target, and the unfocused image of the barrel and bead are placed below the target (the amount below depends on whether the target is rising or falling) and slightly ahead of the target if there is lateral movement. This method of aiming is not as precise as that of a front sight/rear sight combination, but it is much faster, and the wide spread of shot allows a hit even if there is some error in aim. Some shotguns also provide a mid-bead, which is a smaller bead located halfway down the rib, which allows more feedback on barrel alignment.

Weapons Featuring the Iron Sights

 * M7 Caseless SMG
 * M7S Caseless SMG
 * M90 Shotgun Series
 * DTM/Law Enforcement (Possibly)
 * MA5K Carbine (Possibly)
 * M6C Magnum