Cartridge (firearm ammunition)

Main components

Modern metallic cartridges typically include four principal parts. The case is a cylindrical container, commonly manufactured from brass or other metals, that holds everything together. The primer is a small, sensitive charge located at the base that initiates ignition when struck by the firing pin. The propellant, traditionally called gunpowder though modern propellants are smokeless powders, burns rapidly to generate gas pressure. The projectile, most often a bullet, is seated at the mouth of the case and is driven down the barrel by expanding gases. The cartridge is sized to fit the firearm's chamber.

History and development

Cartridges became widely adopted during the nineteenth century as firearms technology moved from separate loading (where powder, wad and ball were loaded separately) to self-contained rounds. The development of metallic cases and reliable primers simplified loading, improved rate of fire, and enhanced safety and storage. Over time designs were refined to provide better sealing, feeding and extraction in repeating rifles, pistols and machine guns.

Types and operation

• Centerfire vs rimfire: In centerfire cartridges the primer sits in a separate component in the case head; in rimfire designs the priming compound is contained in the rim of the case. Rimfire is common for low-pressure rounds.
• Caliber and case shape: Cartridges vary by caliber (projectile diameter) and case geometry—straight, bottlenecked, or tapered designs affect feeding and ballistic performance.
• Specialized loads: Ammunition may be loaded with full metal jacket, soft point, hollow point, shot, or tracer projectiles depending on intended use.

Uses, safety and distinctions

Cartridges are used for military, law enforcement, hunting, sport shooting and personal defense. Handling and storage require attention to legal regulation and safety: keep cartridges dry, avoid excessive heat, and follow local laws. Distinctions often made between a cartridge and the broader term shell: 'shell' can imply larger artillery rounds or shotgun shotshells, whereas 'cartridge' usually denotes the self-contained small arms round.

Understanding components and types helps users select appropriate ammunition for a firearm, ensures compatibility, and promotes safe operation. For further technical and historical detail consult specialist sources and manufacturers' guidance.