What does headspace refer to in the context of a machine gun?

Headspace in the context of a machine gun refers to the distance between the bolt face and the cartridge base when the bolt is locked in the closed position. This measurement is critical to ensure the proper functioning of the firearm.

Having the correct headspace allows the cartridge to be aligned properly within the chamber, ensuring that the firing pin strikes the primer effectively and that there is adequate room for the cartridge to expand during firing without causing a malfunction or damage to the weapon. If the headspace is too short, there is a risk of failure to fire due to the bolt not being able to fully close on the cartridge. Conversely, excessive headspace could lead to problems such as misfires or dangerous high-pressure situations that may result in a catastrophic failure of the firearm.

Understanding headspace is essential for the maintenance and safe operation of machine guns, making it a crucial aspect of gunnery practice.