Cartridges designed for pistols and submachine guns firing projectiles of approximately 9 millimeters diameter are sometimes manufactured with a core of hardened material, such as tungsten carbide or steel, intended to defeat body armor. These projectiles typically feature a jacket of softer metal, like copper or a copper alloy, surrounding the hardened core. A common example would be a 919mm Parabellum cartridge loaded with such a projectile.
The development of such ammunition stems from military and law enforcement requirements to address threats posed by individuals wearing protective gear. Historically, the need for enhanced penetration capabilities has driven innovation in small arms projectile technology, leading to advancements in materials science and projectile design. This has resulted in ongoing debates regarding the balance between public safety and potential misuse.