A gun shield is a flat piece or section of armor designed to be mounted on a crew-served weapon such as a machine gun

Machine gun

A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

 or artillery

Artillery

Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...

 piece, or, more rarely, to be used with an assault rifle

Assault rifle

An assault rifle is a selective fire rifle that uses an intermediate cartridge and a detachable magazine. Assault rifles are the standard infantry weapons in most modern armies...

 or, in a law enforcement context, a semi-automatic pistol.

Military

Some mounted machine guns and artillery pieces are equipped with metal armor plates to protect the gunners from sniper

Sniper

A sniper is a marksman who shoots targets from concealed positions or distances exceeding the capabilities of regular personnel. Snipers typically have specialized training and distinct high-precision rifles....

 fire and shrapnel

Fragmentation (weaponry)

Fragmentation is the process by which the casing of an artillery shell, bomb, grenade, etc. is shattered by the detonating high explosive filling. The correct technical terminology for these casing pieces is fragments , although shards or splinters can be used for non-preformed fragments...

 from explosions. As well, gun shields are sometimes improvised in the field in using salvaged metal plates. The most common examples were seen in the Vietnam War

Vietnam War

The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

 when the crews of armored fighting vehicles and PT Boat

PT boat

PT Boats were a variety of motor torpedo boat , a small, fast vessel used by the United States Navy in World War II to attack larger surface ships. The PT boat squadrons were nicknamed "the mosquito fleet". The Japanese called them "Devil Boats".The original pre–World War I torpedo boats were...

s would affix metal plates to the machine guns, though gun shields have been in use as early as World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

.

Gun shields fell out of widespread use after Vietnam, but they have seen a resurgence in popularity during the 1990s. Israeli military analysts began urging the use of gun shields when they noted that the automatic weapon fire-filled modern battleground presented a grave risk to soldiers who exposed themselves to fire upon the enemy. In particular, it was noted that many casualties were being hit in areas not protected by body armor or the helmet, such as the neck or face.

The U.S. began using gun shields during the 2000s-era conflicts in Iraq and Afghanistan. The major drawback of gun shields is that they limit the visibility of the user to the front, though new designs such as the Transparent Armor Gun Shield

Transparent Armor Gun Shield

Built by BAE Systems, the Transparent Armor Gun shield, or TAGS, is a visually transparent protective gun shield for operators of vehicle-mounted machine guns. It borrows on the experience of the Israeli Defense Force in using such armor on a variety of vehicles. The shield is intended to provide...

 (TAGS for short) will alleviate this without sacrificing user protection.

Law enforcement

When tactical police

SWAT

A SWAT team is an elite tactical unit in various national law enforcement departments. They are trained to perform high-risk operations that fall outside of the abilities of regular officers...

 squads or hostage rescue teams are approaching a heavily-armed suspect or group of suspects, they are increasingly using ballistic glass

Bulletproof glass

Bulletproof glass is a type of strong but optically transparent material that is particularly resistant to being penetrated when struck by bullets, but is not completely impenetrable. It is usually made from a combination of two or more types of glass, one hard and one soft...

 or kevlar

Kevlar

Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...

 gun shields. These shields supplement the protection from the body armor that the officers are already wearing by protecting the exposed body areas such as the neck and face. Gun shields typically have a firing hole or port through which the officer can fire a weapon. Some police officers using gun shields use revolver

Revolver

A revolver is a repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing. The first revolver ever made was built by Elisha Collier in 1818. The percussion cap revolver was invented by Samuel Colt in 1836. This weapon became known as the Colt Paterson...

s instead of semi-automatic pistols, because the slide

Pistol slide

The slide is the part of the weapon on a majority of semi-automatic pistols that moves during the operating cycle and generally houses the firing pin or striker and the extractor, and serves as the bolt...

of a semi-auto pistol tends to get caught in the firing port.