What does the term "headspace" refer to in firearms?

The term "headspace" specifically refers to the distance between the face of the bolt and the base of a cartridge case when the cartridge is fully seated in the chamber. This measurement is critical for the safe and proper functioning of a firearm. Correct headspace ensures that the cartridge is positioned correctly in relation to the firing pin and the chamber, allowing for optimal ignition of the primer when the firearm is discharged.

If the headspace is too short, there may not be enough room for the cartridge to expand fully, which can lead to cylinder seizing or misfires. Conversely, too much headspace can cause excessive movement of the cartridge, potentially resulting in a failure to fire or dangerous over-pressure situations. Therefore, maintaining precise headspace is vital for the reliability and safety of a firearm.