page_title: Headspace (firearms)
hierarchical_section_title: Headspace (firearms)
caption_attribution_description: English: Diagram showing headspace measurement of a .45 ACP semi-automatic pistol
context_page_description: In firearms, headspace is the distance measured from the part of the chamber that stops forward motion of the cartridge to the face of the bolt. Used as a verb, headspace refers to the interference created between this part of the chamber and the feature of the cartridge that achieves the correct positioning. Different cartridges have their datum lines in different positions in relation to the cartridge. For example, 5.56 NATO ammunition headspaces off the shoulder of the cartridge, whereas .303 British headspaces off the forward rim of the cartridge.
  If the headspace is too short, ammunition that is in specification may not chamber correctly. If headspace is too large, the ammunition may not fit as intended or designed and the cartridge case may rupture, possibly damaging the firearm and injuring the shooter.
context_section_description: In firearms, headspace is the distance measured from the part of the chamber that stops forward motion of the cartridge (the datum reference) to the face of the bolt.  Used as a verb, headspace refers to the interference created between this part of the chamber and the feature of the cartridge that achieves the correct positioning.  Different cartridges have their datum lines in different positions in relation to the cartridge.  For example, 5.56 NATO ammunition headspaces off the shoulder of the cartridge, whereas .303 British headspaces off the forward rim of the cartridge.
  If the headspace is too short, ammunition that is in specification may not chamber correctly. If headspace is too large, the ammunition may not fit as intended or designed and the cartridge case may rupture, possibly damaging the firearm and  injuring the shooter.
caption: A pistol cartridge which headspaces off the case mouth, e.g. .45 ACP
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