A breech screw, also referred to as a breech pin or breech plug, is a crucial component in weaponry, specifically in firearms. It serves as a secure closure for the breech (the rear end of the gun barrel). In alternative terms, it can be identified as the breech block or breech bolt, both of which embody the same function of safely sealing the firearm. These synonyms are common within the firearm industry, where precision and accuracy are of utmost importance. Understanding the various terms associated with the breech screw aids in the comprehensive comprehension and discussions surrounding firearms and their mechanisms.