Tracer ammunition (tracers) are bullet

Bullet

A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...

s that are built with a small pyrotechnic charge in their base. Ignited by the burning powder, the phosphorus tail burns very brightly, making the projectile visible to the naked eye. This enables the shooter to follow the bullet trajectory

Trajectory

A trajectory is the path that a moving object follows through space as a function of time. The object might be a projectile or a satellite, for example. It thus includes the meaning of orbit—the path of a planet, an asteroid or a comet as it travels around a central mass...

 relative to the target in order to make aiming corrections.

When used, tracers are usually loaded as every fifth round in machine gun belts, referred to as four-to-one tracer. Platoon

Platoon

A platoon is a military unit typically composed of two to four sections or squads and containing 16 to 50 soldiers. Platoons are organized into a company, which typically consists of three, four or five platoons. A platoon is typically the smallest military unit led by a commissioned officer—the...

 and squad leaders will sometimes load their magazines entirely with tracers to mark targets for their soldiers to fire on. Tracers are also sometimes placed two or three rounds from the bottom of magazines to alert the shooter that their weapon is almost empty.

History

Before the development of tracers, gunners relied on seeing their bullet impacts to adjust their aim. However, these were not always visible. In the early 20th century, ammunition designers developed "spotlight" bullets, which would create a flash or smoke puff on impact to increase their visibility. However, these projectiles were deemed in violation of the Hague Convention's

Hague Conventions (1899 and 1907)

The Hague Conventions were two international treaties negotiated at international peace conferences at The Hague in the Netherlands: The First Hague Conference in 1899 and the Second Hague Conference in 1907...

 prohibition of "exploding bullets." This strategy was also useless when firing at aircraft, as there was nothing for the projectiles to impact on if they missed the target. Designers also developed bullets that would trail white smoke

Smoke

Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...

. However, these designs required an excessive amount of mass loss to generate a satisfactory trail. The loss of mass en route to the target severely affected the bullet's ballistics

Ballistics

Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...

.

The British

British people

The British are citizens of the United Kingdom, of the Isle of Man, any of the Channel Islands, or of any of the British overseas territories, and their descendants...

 introduced a tracer version of the .303 cartridge

.303 British

.303 British, or 7.7x56mmR, is a .311 inch calibre rifle and machine gun cartridge first developed in Britain as a blackpowder round put into service in December 1888 for the Lee-Metford rifle, later adapted to use smokeless powders...

 in 1915. The United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 introduced a .30-06

.30-06 Springfield

The .30-06 Springfield cartridge or 7.62×63mm in metric notation, was introduced to the United States Army in 1906 and standardized, and was in use until the 1960s and early 1970s. It replaced the .30-03, 6 mm Lee Navy, and .30 US Army...

 tracer in 1917. Prior to adopting red and, later, other color bullet tips, for tracers, US tracers were identified by blackened cartridge cases.

Tracers proved useful as a countermeasure

Countermeasure

A countermeasure is a measure or action taken to counter or offset another one. As a general concept it implies precision, and is any technological or tactical solution or system designed to prevent an undesirable outcome in the process...

 against Zeppelin

Zeppelin

A Zeppelin is a type of rigid airship pioneered by the German Count Ferdinand von Zeppelin in the early 20th century. It was based on designs he had outlined in 1874 and detailed in 1893. His plans were reviewed by committee in 1894 and patented in the United States on 14 March 1899...

s used by Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 during 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...

. The airship

Airship

An airship or dirigible is a type of aerostat or "lighter-than-air aircraft" that can be steered and propelled through the air using rudders and propellers or other thrust mechanisms...

s were used for surveillance and bombing operations. Normal bullets merely had the effect of causing a slow leak, but tracers could ignite the hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 gasbags

Balloon

A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig...

, and bring down the airship quickly.
Tracer rounds may also ignite flammable substances.

Construction

A tracer projectile is constructed with a hollow base filled with a pyrotechnic flare material, often made of phosphorus

Phosphorus

Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

 or magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

 or other bright burning chemicals

Pyrotechnic composition

A pyrotechnic composition is a substance or mixture of substances designed to produce an effect by heat, light, sound, gas or smoke or a combination of these, as a result of non-detonative self-sustaining exothermic chemical reactions...

. In US

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

  and NATO standard ammunition, this is usually a mixture of strontium

Strontium

Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...

 compounds (nitrate

Strontium nitrate

Strontium nitrate is an inorganic compound with the formula Sr2. This colourless solid is used as an colorant in pyrotechnics.- Preparation:Strontium nitrate is typically generated by the reaction of nitric acid on strontium carbonate.....

, peroxide

Strontium peroxide

Strontium peroxide is a whitish inorganic compound, a peroxide of strontium. It is an oxidizing agent used for bleaching. It is used in some pyrotechnic compositions as an oxidizer and a vivid red pyrotechnic colorant. Its CAS number is ....

, etc.) and a metal fuel such as magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

. This yields a bright red light. Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

n and Chinese

People's Republic of China

China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

 tracer ammunition generates red or green light using barium

Barium

Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...

 salts. It is not true that they use only green tracers even if identified by green bullet tips. Some modern designs use compositions that produce little to no visible light and radiate mainly in infrared, being visible only on night vision

Night vision

Night vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range...

 equipment.

Tracers can never be a totally reliable indicator of a gunner's aim, since all tracer rounds have different aerodynamics

Aerodynamics

Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...

 and weight from ordinary rounds. Over long ranges, the stream of tracer rounds and the stream of ordinary rounds will diverge significantly. This is caused by a tracer bullet's mass decreasing during flight, because the tracer material in its base burns and vaporizes. Although advances in tracer design have diminished this problem, it cannot be completely eliminated.

Types

There are three types of tracers: bright tracer, subdued tracer and dim tracer. Bright tracers are the standard type, which start burning immediately after exiting the muzzle. A disadvantage of bright tracers is that they give away the shooter's location to the enemy; as a military adage puts it, "tracers work both ways". Bright tracers can also overwhelm night-vision devices, rendering them useless. Subdued tracers burn at full brightness after a hundred or more yards to avoid giving away the gunner's position. Dim tracers burn very dimly but are clearly visible through night-vision equipment.

The M196 tracer cartridge (55-grain bullet) is a training round for 5.56mm NATO weapons. It has a red tip and is designed to trace out to 500 yards.

The M856 tracer cartridge (63.7-grain bullet) is used in the M16A2/3/4, M4-series

M4 carbine

The M4 carbine is a family of firearms tracing its lineage back to earlier carbine versions of the M16, all based on the original AR-15 designed by Eugene Stoner and made by ArmaLite. It is a shorter and lighter variant of the M16A2 assault rifle, with 80% parts commonality.It is a gas-operated,...

, and M249 weapons (among other 5.56mm NATO weapons). This round is designed to trace out to 875 yards and has a red tip (orange when linked 4 to 1 with the M249). It is not to be used in the M16A1 except under emergency conditions and at ranges of less than 90 meters, because the M16A1's rifling twist is not sufficient to stabilize the projectile. The M16A2 rifle has a rifling twist of 1 in 7" to stabilize the M856 tracer rounds (since the M856 is slightly longer than the M196).

The M25 is a 30.06 tracer cartridge consisting of a 145 gr bullet with 50 grains of IMR 4895 powder. Orange tip. The tracer compound contains composition R 321 which is 16% polyvinyl chloride

Polyvinyl chloride

Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...

, 26% magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

 powder, 52% strontium nitrate

Strontium nitrate

Strontium nitrate is an inorganic compound with the formula Sr2. This colourless solid is used as an colorant in pyrotechnics.- Preparation:Strontium nitrate is typically generated by the reaction of nitric acid on strontium carbonate.....

.

The M62 is a 7.62x51mm NATO tracer consisting of a 142 gr bullet with 46 grains of WC 846 powder. Orange tip. The tracer compound contains composition R 284 which is 17% polyvinyl chloride, 28% magnesium powder, and 55% strontium nitrate. (This is the same composition used on the M196.)

The M276 is a dim tracer that uses composition R 440, which is barium peroxide

Barium peroxide

Barium peroxide is the chemical compound with the formula BaO2. This grey-white solid is one of the most common inorganic peroxides. Barium peroxide is an oxidizing agent, which is used for bleaching...

, strontium peroxide

Strontium peroxide

Strontium peroxide is a whitish inorganic compound, a peroxide of strontium. It is an oxidizing agent used for bleaching. It is used in some pyrotechnic compositions as an oxidizer and a vivid red pyrotechnic colorant. Its CAS number is ....

, calcium resinate for example calcium abietate, and magnesium carbonate

Magnesium carbonate

Magnesium carbonate, MgCO3, is a white solid that occurs in nature as a mineral. Several hydrated and basic forms of magnesium carbonate also exist as minerals...

. Violet tip.

Tracer compositions can also emit primarily in infrared

Infrared

Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

, for use with night-vision devices. An example composition is boron

Boron

Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...

, potassium perchlorate

Potassium perchlorate

Potassium perchlorate is the inorganic salt with the chemical formula KClO4. Like other perchlorates, this salt is a strong oxidizer and potentially reacts with many organic substances...

, sodium salicylate

Sodium salicylate

Sodium salicylate is a sodium salt of salicylic acid. It can be prepared from sodium phenolate and carbon dioxide under higher temperature and pressure...

, iron carbonate or magnesium carbonate

Magnesium carbonate

Magnesium carbonate, MgCO3, is a white solid that occurs in nature as a mineral. Several hydrated and basic forms of magnesium carbonate also exist as minerals...

 (as combustion retardant), and binder. Many variants exist.http://www.faqs.org/patents/app/20080257194

Other applications

Tracers can also serve to direct fire at a given target, because it is visible to other combatants. The disadvantage is that they betray the gunner's position; the tracer path leads back to its source. To make it more difficult for an enemy to do this, most modern tracers have a delay element

Delay composition

Delay composition, also called delay charge or delay train, is a pyrotechnic composition, a sort of pyrotechnic initiator, a mixture of oxidizer and fuel that burns in a slow, constant rate that should not be significantly dependent on temperature and pressure. Delay compositions are used to...

, which results in the trace becoming visible some distance from the muzzle. Its lethality is similar to conventional ammunition. However, the mass loss and the burning aspects can make the consequences of the impact slightly different.

Besides guiding the shooter's direction of fire, tracer rounds can also be loaded at the end of a magazine

Magazine (firearm)

A magazine is an ammunition storage and feeding device within or attached to a repeating firearm. Magazines may be integral to the firearm or removable . The magazine functions by moving the cartridges stored in the magazine into a position where they may be loaded into the chamber by the action...

 to remind the shooter that the magazine is almost empty. This is particularly useful in weapons that do not lock the bolt back when empty (such as the AK-47

AK-47

The AK-47 is a selective-fire, gas-operated 7.62×39mm assault rifle, first developed in the Soviet Union by Mikhail Kalashnikov. It is officially known as Avtomat Kalashnikova . It is also known as a Kalashnikov, an "AK", or in Russian slang, Kalash.Design work on the AK-47 began in the last year...

). During World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, the Soviet Air Force

Soviet Air Force

The Soviet Air Force, officially known in Russian as Военно-воздушные силы or Voenno-Vozdushnye Sily and often abbreviated VVS was the official designation of one of the air forces of the Soviet Union. The other was the Soviet Air Defence Forces...

 also used this practice for aircraft machine guns. One disadvantage in this practice is that the enemy is alerted that the pilot or shooter is low on ammunition and possibly vulnerable. For ground forces

Ground Forces

The Hungarian Ground Forces are one of the branches of the Hungarian armed forces. It is the army which handles Ground activities and troops including artillery, tanks, APC's, IFV's and ground support...

, this generally offers no tactical advantage to the enemy, since a soldier who is out of ammunition is supposed to alert his team that he is "dry" and rely on their support while he reloads. Thus, an enemy must risk exposing himself in order to attack the reloading soldier. Modern aircraft tend to rely on missile

Missile

Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...

s, radar

Radar

Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

, or laser-guided sights to track the enemy, thereby making the use of tracers less essential.

Safety restrictions

In the UK, usage of tracer rounds is restricted on National Rifle Association of the United Kingdom

National Rifle Association of the United Kingdom

The National Rifle Association of the United Kingdom is the governing body of full bore rifle and pistol shooting sports in the United Kingdom.- History :...

-operated ranges, due to an increased risk of fire. Unauthorized use will be punished at the discretion of the acting range officer. Use of tracers is usually only authorized during military training.

In July 2009, a large fire was started by tracer ammunition near Marseille

Marseille

Marseille , known in antiquity as Massalia , is the second largest city in France, after Paris, with a population of 852,395 within its administrative limits on a land area of . The urban area of Marseille extends beyond the city limits with a population of over 1,420,000 on an area of...

, France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, an area where shrub vegetation is very dry and flammable in the summer, and where normally this kind of ammunition should not be used.

External links

• 2010 article with photographs of tracers at night
• European Ammunition Box Translations
• Video of Kord machine gun
  Kord machine gun
  The Kord-12.7 mm heavy machine gun is a Russian design that entered service in 1998 replacing the older NSV machine gun. Externally the weapon resembles the NSV, however the internal mechanism has been extensively reworked, changing from a horizontally pivoting breech block to a rotating bolt...
  
   shooting tracer ammunition from official website of Degtyaryov plant.
• M25 and M62 (.30 caliber) tracer bullet analysis.