Armor-piercing bullet

Armor-piercing bullets typically contain a hardened steel, tungsten, or tungsten carbide penetrator encased within a copper or cupronickel jacket, similar to the jacket which would surround lead in a conventional projectile. The penetrator is a pointed mass of high-density material designed to retain its shape and carry the maximum possible amount of energy as deeply as possible into the target. The entire projectile is not normally made of the same material as the penetrator because the hard metals of good penetrators would damage the barrel of the gun firing the bullet. Impact velocity of the copper jacket may temporarily soften the face of the armor and cushion the impact to avoid breaking the brittle penetrator. The penetrator then slides out of the jacket to continue forward through the armor.[1]

Handgun bullets made entirely of lead have less penetration ability than jacketed bullets at similar velocity. In the 1930s, Western Cartridge Company introduced .38 Special ammunition capable of firing a 158-grain (10.2 g) copper-tipped lead-alloy bullet at 1,125 feet (343 m) per second to penetrate sheet-metal automobile doors.[4] As higher velocity handgun cartridges became available and jacketed bullets became more common in handgun cartridges, armor penetration was improved with thicker bullet jackets or bullets made entirely of jacket material like copper or brass. Later designs used penetrator cores similar to rifle designs.[1] Some of these bullets were coated with Teflon to reduce their tendency to ricochet off glass or sheet metal.[5]