Armor-piercing (AP) ammunition has a projectile or projectile core constructed entirely from a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium. The most effective AP bullets are usually confined to rifle bullets, as velocity and range are important factors in AP requirements. Some revolver and pistol ammunition is described as metal piercing but, although it would be effective against vehicle bodywork and some body armor, it would be ineffective against "heavy" armor plate. AP bullets are, with very few exceptions, jacketed.
AP rifle bullets usually have a bullet tip filler (usually lead) which is designed to "cushion" the effect of the impact on the AP core, which is very hard and brittle and can break on impact without a "cushioning" effect. The AP core is also frequently surrounded with a thin sheath of lead between the core and the bullet jacket. The AP core is usually hardened steel such as tungsten/carbon, tungsten/chromium, manganese/molybdenum, chromium/vanadium, or chromium/molybdenum.
Two specifications for AP core material are:
1. Steel with 2% to 3% tungsten and 1.25% carbon
2. Steel with 3% to 4% tungsten, 1.1% carbon, and a trace of manganese67
Tungsten carbide has also been used as an AP core and gives much superior penetration. It is produced by alloying tungsten with carbon, nickel, cobalt, or other elements. Tungsten carbide is about twice as dense as steel and about 1.4 times denser than lead. It is nonmagnetic and extremely hard. Analysis of such a core yielded the following results:
+ trace elements
A tungsten carbide AP bullet which also incorporates a lachrymal agent and a tungsten carbide AP core/tracer/tear gas bullet have been manufactured. A similar AP/tracer/tear gas bullet was also manufactured with hardened steel, rather than a tungsten carbide core.
There is a Chinese tungsten carbide AP bullet with a discarding sabot which is very effective due to its very high velocity. The United States also produced an AP bullet with a discarding sabot using depleted uranium as the bullet core material.68
Revolver and pistol metal-piercing bullets are available in a range of calibers and designs:
KTW bullet: The original design had a hard steel or tungsten steel core with a copper gas check and the current version is a solid brass or bronze bullet without a gas check. Both have a gliding metal half jacket and the exposed portion of the bullet is coated with green-colored Teflon.
National bullet: A sharply pointed solid steel bullet the base of which is contained within a brass cup.
ABC (American Ballistic Company) bullet: A solid steel-pointed bullet without a jacket.
Arcane bullet: A cone-shaped flat base bullet made from solid copper alloy (the .380" caliber is round nosed).
THV bullet (Tres Haute Vitesse): An unusually shaped bullet made of solid brass with three times more penetrating power than a conventional bullet due to its hardness, geometric design, and high velocity.
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