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A full metal jacket (FMJ) bullet is a small-arms projectile consisting of a soft core (often
A full metal jacket (FMJ) bullet is a small-arms projectile consisting of a soft core (often lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
) encased in an outer shell ("jacket") of harder metal, such as gilding metal
Gilding metal is a form of brass (an alloy of copper and zinc) with a much higher copper content than zinc content. Exact figures range from 95% copper and 5% zinc to “8 parts copper to 1 of zinc” (11% zinc) in British Army Dress Regulations.
...
, cupronickel
Cupronickel or copper-nickel (CuNi) is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese. The copper content typically varies from 60 to 90 percent. ( Monel is a nickel-copper alloy that contains a mi ...
, or, less commonly, a steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistan ...
alloy. A bullet jacket usually allows higher muzzle velocities
Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately to i ...
than bare lead without depositing significant amounts of metal in the bore. It also prevents damage to bores from hard steel or armor-piercing
Armour-piercing ammunition (AP) is a type of projectile designed to penetrate either body armour or vehicle armour.
From the 1860s to 1950s, a major application of armour-piercing projectiles was to defeat the thick armour carried on many warsh ...
core materials.
History
The bullet was invented in 1882 by Swiss ColonelEduard Rubin
Eduard Alexander Rubin (17 July 1846 – 6 July 1920) was a Swiss mechanical engineer who is most notable for having invented the full metal jacket bullet in 1882. His most famous cartridge was the 7.5×55mm Swiss which was the standard am ...
while he was working for the Swiss Federal Ammunition Factory and Research Center, which developed ammunition for the Swiss military.
The use of full metal jacketing in military ammunition came about in part because of the need for improved feeding characteristics in small arms that used internal mechanical manipulation of the cartridge in order to chamber rounds as opposed to externally hand-reloading single-shot firearms. The harder metal used in bullet jackets was less prone to deformation than softer exposed lead, which improved feeding. That also allowed bullets to withstand much higher velocities caused by the decrease of the caliber.
It is sometimes thought that military use of FMJ ammunition was the result of The Hague Convention of 1899, Declaration III, prohibiting the use in international warfare of bullets that easily expand or flatten in the body. However, jacketed bullets were adopted by most European militaries during the late 1880s and early 1890s, about a decade prior to the Hague Convention.
Impact characteristics
By design, fully jacketed projectiles have less capacity to expand after contact with the target than a hollow-point projectile. While this can be an advantage when engaging targets behind cover, it can also be a disadvantage as an FMJ bullet may pierce completely through a target, leading to less severe wounding, and possibly failing to disable the target. Furthermore, a projectile that goes completely through a target can cause unintentionalcollateral damage
Collateral damage is any death, injury, or other damage inflicted that is an incidental result of an activity. Originally coined by military operations, it is now also used in non-military contexts.
Since the development of precision guided ...
behind the target.
See also
*Soft-point bullet
A soft-point bullet (SP), also known as a soft-nosed bullet, is a jacketed expanding bullet with a soft metal core enclosed by a stronger metal jacket left open at the forward tip. A soft-point bullet is intended to expand upon striking flesh to ...
* Total metal jacket
References
External links
* * * {{Handloading Bullets