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Full metal jacket (ammunition)

Type of bullet with a harder outer shell

Full metal jacket (ammunition)

Type of bullet with a harder outer shell

These .30-caliber (7.62 mm) full metal jacket bullets show the typical jacket openings exposing the lead alloy core on the base of the bullet to illustrate that a full metal jacket may not completely enclose the core.

A full metal jacket (FMJ) bullet is a small-arms projectile consisting of a soft core (often lead) encased in an outer shell ("jacket") of harder metal, such as gilding metal, cupronickel, or, less commonly, a steel alloy. A bullet jacket usually allows higher muzzle velocities than a lead alloy cast bullet without depositing significant amounts of metal in the bore. It also prevents damage to bores from hard steel or armor-piercing core materials.

History

Despite a widespread belief that the full metal jacket bullet was invented ca. 1882 by Swiss Colonel Eduard Rubin while he was working for the Swiss Federal Ammunition Factory and Research Center, in fact it was known already in the 1880s that the actual inventor was Prussian Major (later Lt.-Col.) (1835–1885), who came up with the idea in either 1875 or 1876.

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. Full metal jacketing also allowed bullets to withstand much higher velocities caused by the decrease of the caliber.

In addition to the various advantages afforded by FMJ rounds, the Hague Convention of 1899 Declaration III prohibits in international warfare the use of bullets that easily expand or flatten in the body.

Impact characteristics

By design, a fully jacketed projectile has less capacity to expand after contact with the target than a hollow-point projectile or a soft-point projectile. Although that can be an advantage when engaging targets behind cover, it can also be a disadvantage because an FMJ bullet may pierce completely through a target, leading to less-severe wounding and, possibly, failure to disable the target. Furthermore, a projectile that goes completely through a target can cause unintentional damage behind the target.

References

References

  1. Huon, Jean. (1988). "Military Rifle and Machine Gun Cartridges". Ironside International.
  2. "Swiss Handguns 1882".
  3. Holt Bobinson. (November 2008). "The model 1911 Schmidt Rubin: the other Switzer". Guns Magazine.
  4. Wood, J. B.. (2003). "The Gun Digest Book of Firearms Assembly/Disassembly: Centerfire Rifles, Volume 4". Krause Publications.
  5. (1885). "Archiv für die Artillerie- und Ingenieur-Offiziere des deutschen Reichsheeres". Mittler.
  6. "'Das Kleinste Kaliber oder das zukünftige Infanteriegewehr. 1/2' - Viewer {{pipe".
  7. (1889). "Monatshefte für Politik und Wehrmacht".
  8. (1887). ""Der" Kamerad Wien, 1862 - 1896: österreichisch-ungarische Wehr-Zeitung".
  9. (1882). "Die Repetir-Gewehre: ihre Geschichte, Entwickelung, Einrichtung und Leistungsfähigkeit; unter besonderer Berücksichtigung amtlicher Schiessversuche und mit Benutzung von Originalwaffen dargestellt". Zernin.
  10. Ramage, C. Kenneth. (1980). "Lyman Cast Bullet Handbook". Lyman Publications.
  11. (1949). "The Belding & Mull Handbook". Belding & Mull.
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