Editing Breechblock (section)

{{Short description|Part of the firearm action}}
[[File:Firearm actions.svg|thumb|400px|right|Illustration of some firearm breechblocks]]
A '''breechblock''' (or '''breech block''') is the part of the [[firearm action]] that closes the [[Breech (firearms)|breech]] of a [[breech loading]] weapon (whether [[small arms]] or [[artillery]]) before or at the moment of firing.  It seals the breech and contains the pressure generated by the ignited [[propellant]]. Retracting the breechblock allows the [[Chamber (firearms)|chamber]] to be loaded with a [[Cartridge (firearms)|cartridge]].

Breechblocks are categorised by the type or design of the mechanism by which it is locked or closed for firing.  The firearm action more fully refers to the mechanism by which the operator actuates the opening and closing of the breech.