The Picatinny rail or MIL-STD-1913 rail or STANAG

STANAG

STANAG is the NATO abbreviation for Standardization Agreement, which sets up processes, procedures, terms, and conditions for common military or technical procedures or equipment between the member countries of the alliance. Each NATO state ratifies a STANAG and implements it within their own...

 2324 rail or a "Tactical Rail" is a bracket used on some firearm

Firearm

A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...

s in order to provide a standardized mounting platform. A similar system is the Weaver rail mount

Weaver rail mount

A Weaver rail mount is a system to connect telescopic sights and other accessories to rifles, shotguns, pistols, archery bows, etc...

.

Description

The rail comprises a series of ridges with a T-shaped cross-section interspersed with flat "spacing slots". Scopes are mounted either by sliding them on from one end or the other; by means of a weaver mount which is clamped to the rail with bolts, thumbscrews or levers; or onto the slots between the raised sections.

History

Picatinny’s role with the rail was to test/evaluate it and to create a military standard for it. This was Mil-STD-1913 rail date 3 February 1995.

Specifications for the M16A2E4 rifle and the M4E2 carbine received type classification generic in December 1994. These were the M16A2 and the M4 modified with the rails replacing hand guards.

The rail itself dates from work by the A.R.M.S. company in the early 1980s

Uses

The rail was originally for scopes. However, once established, the use of the system was expanded to other accessories, such as tactical light

Tactical light

A tactical light is a flashlight used in conjunction with a firearm to aid low light target identification, allowing the marksman to simultaneously aim and illuminate the target. Tactical lights can be handheld or mounted to the weapon with the light beam parallel to the bore...

s, laser aiming modules, night vision devices, reflex sights, foregrip

Foregrip

A foregrip is the grip on the front of a firearm that helps to control the gun, and prevent burns from the barrel during firing. A vertical foregrip can also allow for easier horizontal movement of the firearm, as it creates a firmer grasping point than conventional hand guards. Some firearms...

s, bipod

Bipod

A bipod is a support device that is similar to a tripod or monopod, but with two legs. It provides significant stability along two axes of motion .-Firearms:...

s, and bayonet

Bayonet

A bayonet is a knife, dagger, sword, or spike-shaped weapon designed to fit in, on, over or underneath the muzzle of a rifle, musket or similar weapon, effectively turning the gun into a spear...

s. Because they were originally designed and used for telescopic sight

Telescopic sight

A telescopic sight, commonly called a scope, is a sighting device that is based on an optical refracting telescope. They are equipped with some form of graphic image pattern mounted in an optically appropriate position in their optical system to give an accurate aiming point...

s, the rails were first used only on the receiver

Receiver (firearms)

In firearms terminology, the receiver is the part of a firearm that houses the operating parts. The receiver usually contains the bolt carrier group, trigger group, and magazine port. In most handguns, the receiver, or frame, holds the magazine well or rotary magazine as well as the trigger mechanism...

s of larger caliber rifle

Rifle

A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...

s. But their use has extended to the point that Picatinny rails and accessories have replaced iron sights

Iron sights

Iron sights are a system of shaped alignment markers used as a sighting device to assist in the aiming of a device such as a firearm, crossbow, or telescope, and exclude the use of optics as in telescopic sights or reflector sights...

 in the design of many firearms, and they are also incorporated into the undersides of semi-automatic pistol frames and even on grips.

Technical specifications

In order to provide a stable platform, the rail should not flex as the barrel heats and cools; this is the purpose of the spacing slots: they give the rail considerable room to expand and contract lengthwise without distorting its shape. The Picatinny locking slot width is 0.206 in (5.23 mm). The spacing of slot centers is 0.394 in (10.01 mm) and the slot depth is 0.118 in (3 mm). The only differences between the Picatinny rail and the similar Weaver rail

Weaver rail mount

A Weaver rail mount is a system to connect telescopic sights and other accessories to rifles, shotguns, pistols, archery bows, etc...

are the size of these slots and the fact that they are standardized. Weaver rails have a slot width of 0.18 in (4.57 mm), but are not necessarily consistent in the spacing of slot centers. Some accessories are designed to fit on both Weaver and Picatinny rails; but most Picatinny devices will not fit on Weaver rails.