Armor-piercing bullet

This is due to the longer period of acceleration available within the longer gun barrel of rifles, which allow adequate time for the propellant to fully ignite before the projectile exits the barrel.

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.

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.

[1] Some of these bullets were coated with Teflon to reduce their tendency to ricochet off glass or sheet metal.