hylsykotelosta

Hylsykotelosta, also known as a cartridge case or shell casing, is a container that holds the propellant, projectile, and primer of a firearm cartridge. Its primary function is to seal the breech of the firearm during firing, preventing the escape of hot gases and directing them rearward to act on the bolt or bolt carrier. This action enables the firearm's cycling mechanism.

Cartridge cases are typically made from brass, though steel, aluminum, and even plastic are also used depending on the application and cost considerations. The material's properties are crucial; it must be strong enough to withstand the immense pressure generated during firing, yet ductile enough to expand slightly upon firing, forming a gas seal against the chamber walls, and then contract sufficiently to allow for extraction.

The design of a hylsykotelosta varies depending on the firearm and ammunition type. Common features include a rim or extractor groove for engaging the firearm's extractor mechanism, a body to contain the powder charge, and a primer pocket at the base to hold the primer. Different case head designs, such as rimmed, semi-rimmed, rimless, and rebated, are used to facilitate feeding and extraction in various firearm actions. After firing, the spent hylsykotelosta is ejected from the firearm. Reloading of spent casings is a common practice for some ammunition types, allowing for the reuse of the case.