Trigger bar

In a firearm action, the trigger bar is a flat metal piece that is used in some designs to connect the trigger and the sear. The pressure ("pull") on the trigger through the bar causes a movement of the sear that releases the shot.^[1] Most modern semi-automatic pistols use the trigger bar in their actions.^{[citation needed]}

AI-generated sketch of Glock-like pistol trigger bar attached (on the left) to the trigger

The early small arms with matchlock used a long bar instead of a trigger. This bar is also known in the literature as a trigger bar. It was replaced by a short trigger resembling the modern one in the end of the 16th century, with its shape preserved for many more years in the outline of a trigger guard.^[2]

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  16th century trigger bar
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  AI-generated sketch of a Beretta-like pistol trigger bar

Glock

In Glock pistols, the trigger bar is a complex 3D-shaped component essential to the trigger system. When the trigger is pulled, the bar moves backwards and downwards to perform three historically separate functions: it tensions the striker spring, locks the firing pin, and releases the firing pin (working like a sear). The trigger bar also deactivates safeties during the trigger pull, removing the need for manual safeties and thus reducing the chance of a user error.^[3]

Main article: Glock switch

Glock design allows relatively simple conversion of the pistol to the fully automatic fire. After a shot, the striker is prevented from firing again by the cruciform structure at the back end of the trigger bar. If the cruciform is disengaged from the firing pin at the proper time, the gun will fire again without the release of the trigger. While Glock manufactures the Glock 18 model with an automatic fire selector, multiple aftermarket parts for select fire conversion ("Glock switches") are available since the 1990s. A U.S. patent 5,705,763 (1998) describes one of these implementations.^[4]