![Breech Block for a Sig Sauer P220 Breech Block for a Sig Sauer P220](https://jg3ca7.p3cdn1.secureserver.net/wp-content/uploads/2019/03/Breech-Block-for-a-Sig-Sauer-P220.jpg)
Breechblock (Breech Block):
A breechblock (breech block) is the part of a firearm that closes the breech of a weapon at the moment of firing. This prevents the rearward escape of gases. A breechblock must close against the breech for firing but be able to be retracted or otherwise moved for loading or unloading or to remove a spent cartridge.