Armor-piercing ammunition is used to penetrate hardened armored targets such as body armor, vehicle armor, concrete, tanks and other defenses, depending on the caliber. In construction, concrete is a composite building material made from the combination of aggregate and a cement binder.

Armor-piercing ammunition consists of a hardened steel, tungsten-carbide, or depleted-uranium penetrator enclosed within a softer material, such as copper or aluminum. Armor-piercing ammunition can range from rifle and pistol caliber rounds all the way up to tank rounds.

A tank is a tracked armored fighting vehicle, designed primarily to engage enemy forces by the use of direct fire. A tank is characterized by heavy weapons and armor, as well as by a high degree of mobility that allows it to cross rough terrain at relatively high speeds. While tanks are expensive to operate and logistically demanding, they are among the most formidable and versatile weapons of the modern battlefield, both for their ability to engage other ground targets and their shock value against infantry.

Rifle and pistol rounds are usually built around a penetrator of steel or tungsten. Aircraft and tank rounds sometimes use a core of depleted uranium. This penetrator is a pointed mass of high-density material that is designed to retain its shape and carry the maximum possible amount of energy as deep as possible into the target. Depleted-uranium penetrators have the advantage of being pyrophoric and self-sharpening on impact, resulting in incredible heat and energy focused on a minimal area of the target's armor.

Rifle armor-piercing ammunition generally carries its hardened penetrator within a copper or cupro-nickel jacket, similar to the jacket that would surround lead in a conventional projectile. Upon impact on a hard target, the copper case is destroyed, but the penetrator continues its motion and penetrates the substance. Similar armor-piercing ammunition for pistols has also been developed. It is of similar design to the rifle ammo above.

The entire projectile is not normally made of the same material as the penetrator because the physical characteristics that make a good penetrator (tough, hard metal) make the material equally harmful to the barrel of the gun firing the round.

Contrary to common belief, teflon or other coatings on the bullet do not in any way help it penetrate deeper. Teflon-coated bullets were meant to help reduce the wear on the barrel as a result of normal operation. Teflon coating was a trend that has largely faded, in part because of laws resulting from this isconception; there was a brief moral panic over these 'cop-killer bullets', which were said to have been designed to penetrate the body armor worn by police. A moral panic is a mass movement based on the false or exaggerated perception that some cultural behavior or group of people, frequently a minority group or a subculture, is dangerously deviant and poses a menace to society. It has also been more broadly defined as an episode, condition, person or group of persons that has in recent times been defined as a threat to societal values and interests.