tändhylsa

A tändhylsa, which translates to "primer pocket" or "primer seating" in English, is a term used in the context of firearms ammunition, specifically for metallic cartridges. It refers to the recess or cavity at the base of a cartridge case designed to hold the primer. The primer is a small, sensitive explosive device that, when struck by the firing pin of a firearm, initiates the main propellant charge within the cartridge case.

The design and dimensions of the tändhylsa are critical for the proper functioning of a firearm. It must be precisely machined to ensure the primer is seated correctly, neither too deep nor too shallow. If a primer is seated too deeply, it can protrude into the cartridge case, potentially interfering with the bolt's ability to close or, in some firearm designs, causing a "slam-fire" when the bolt is closed. Conversely, if the primer is not seated deeply enough, the firing pin may not be able to strike it with sufficient force to initiate ignition, leading to a misfire.

The tändhylsa is also a key consideration in cartridge reloading. Reloaders must ensure that spent primers are fully removed from the tändhylsa and that new primers are seated to the correct depth. Different types of primers exist, such as small rifle, large rifle, small pistol, and large pistol, and their respective tändhylsor are manufactured to accommodate these variations. The presence of a tändhylsa is a defining characteristic of centerfire ammunition, distinguishing it from rimfire ammunition where the primer compound is located in the rim of the cartridge case itself.