When should headspace be checked on a machine gun?

Headspace should be checked on a machine gun after assembly prior to firing to ensure the weapon is functioning safely and effectively. Headspace refers to the distance between the face of the bolt and the part of the chamber that stops the forward movement of the cartridge. If the headspace is incorrect, it can lead to misfires, ammunition failures, and potential safety hazards, such as excessive pressure when firing.

Performing this check after assembly is crucial because any changes or adjustments made during assembly—whether they involve new parts or simply reassembling components—can affect the headspace configuration. By verifying the headspace before the first round is fired, operators ensure that the machine gun is safe and functional, thus allowing for accurate firing and reliable performance during operations.

Other options may suggest checking headspace at times that may not ensure safety or reliability, as they do not prioritize the necessary pre-firing checks that are integral to combat readiness and equipment safety.