A full metal jacket is a 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...

 consisting of a soft core (usually made of lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

) encased in a shell of harder metal, such as gilding metal

Gilding metal

Gilding metal is a copper alloy, comprising 95% copper and 5% zinc. Technically, it is a brass.Gilding metal is used for various purposes, including the jackets of bullets, driving bands on some artillery shells, as well as enameled badges and other jewellery....

, cupronickel

Cupronickel

Cupronickel or copper-nickel or "cupernickel" is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese. Cupronickel is highly resistant to corrosion in seawater, because its electrode potential is adjusted to be neutral with regard to seawater...

 or less commonly a steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 alloy. This shell can extend around all of the bullet, or often just the front and sides with the rear left as exposed lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

. (A bullet that is completely enclosed by the shell is alternatively termed a total metal jacket round.) The jacket allows for higher muzzle velocities

Muzzle velocity

Muzzle velocity is the speed a projectile has at the moment it leaves the muzzle of the gun. Muzzle velocities range from approximately to in black powder muskets , to more than in modern rifles with high-performance cartridges such as the .220 Swift and .204 Ruger, all the way to for tank guns...

 than bare lead without depositing significant amounts of metal in the bore

Gauge (bore diameter)

The gauge of a firearm is a unit of measurement used to express the diameter of the barrel. Gauge is determined from the weight of a solid sphere of lead that will fit the bore of the firearm, and is expressed as the multiplicative inverse of the sphere's weight as a fraction of a pound . Thus...

. It also prevents damage to bores from steel or armor-piercing core materials. The appearance of FMJ ammunition is highly distinctive when compared to hollow-point or soft point

Soft point bullet

A soft-point bullet , also known as a soft-nosed bullet, is a lead expanding bullet with a copper or brass jacket that is left open at the tip, exposing some of the lead inside and is thus an example of a semi-jacketed round...

 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. Historically, the first successful full metal jacket rifle bullets were invented by Lt. Col. Eduard Rubin

Eduard Rubin

Lieutenant Colonel Eduard Rubin was a Swiss firearm designer who is most notable for inventing the full metal jacket bullet in 1882. His most famous cartridge was the 7.5x55mm Swiss. He served as director of the Swiss Federal Ammunition Factory and Research Center in Thun.-References:...

 of the Swiss Army in 1882. Full metal jacket bullets were first used as standard ammunition in 1886, for the French Mle 1886 Lebel rifle

Lebel Model 1886 rifle

The Lebel Model 1886 rifle is also known as the "Fusil Mle 1886 M93", after a bolt modification was added in 1893. It is an 8mm bolt action infantry rifle which entered service in the French Army in April 1887...

.

Disadvantages

There are some disadvantages to jacketing a bullet. For instance, Full Metal Jacket bullets have different properties, both in terms of behavior inside the barrel of the gun and also in flight. Whereas hollow point and soft-tipped bullets are designed to expand upon impact, full metal jacket bullets are limited in their capacity to expand. This makes the bullet pierce through, in many cases this leads to decreased target damage. Hollow point and soft tipped bullets are for use against soft targets only, such as game or people, whereas Full Metal Jacket bullets can be indiscriminately used against soft and hard targets, delivering sub-optimal damage to both kinds of targets. Jacketed bullets require a certain velocity for proper expansion based on its size, and larger quantity of gunpowder

Gunpowder

Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...

 must be needed. They are the most expensive followed by plated bullets and last cast. Jacketed also are bulkier, heavier and a handful to carry which it has a bigger volume and space occupation. Rifles using this bullet must have large fitting magazine and speedloader

Speedloader

A speedloader is a device used for loading a firearm or firearm magazine that will run out of ammunition very quickly. Generally, speedloaders are used for loading all chambers of a revolver simultaneously, although speedloaders are also used for the loading of fixed tubular magazines of shotguns...

 capacity to insert it easier.

FMJ with variable cores

Some designs of FMJ rifle ammunition inflict more destructive gunshot wounds than others. Not all FMJ bullets contain a simple lead filling. Here are some examples:

Although British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 Mark 7 .303 ammunition

.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...

 is compliant with the terms of the Hague Convention

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...

, it creates more destructive gunshot wounds than standard spitzer bullets due to its internal design. The centre of gravity of the Mark 7 bullet is deliberately shifted towards the rear. This is achieved by constructing the front third of the interior of the bullet from a lighter material such as aluminium

Aluminium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 or wood pulp

Wood pulp

Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...

. The result is a tail-heavy FMJ bullet which yaws

Flight dynamics

Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control systems for...

 violently after hitting the target. The .303 British Mark 7 ammunition has been replaced by the 7.62x51mm NATO

7.62×51mm NATO

The 7.62×51mm NATO is a rifle cartridge developed in the 1950s as a standard for small arms among NATO countries...

External links

• Declaration (IV, 3) concerning Expanding Bullets, made at the 1899 International Peace Conference at The Hague, which entered into force on September 4, 1900
• European Ammunition Box Translations
• Photos showing terminal effects of British Mark 7 .303 bullets