Auto sear

{{Short description|Firearm component}}

An auto sear ("automatic sear") is a part of an automatic firearm that holds the hammer in the cocked position while the bolt of the weapon is cycling and releases the hammer/striker. It is basically an internal trigger actuated by the bolt/bolt carrier when placed in-battery. An auto sear is required in nearly every automatic rifle.

An auto sear allows a semi-automatic gun to be converted into one capable of automatic firing with a single, continuous pull of the trigger. The Bureau of Alcohol, Tobacco, Firearms and Explosives designated any firearm capable of firing more than one round with a single operation of the trigger mechanism as a "machine gun", and the possession of such devices is illegal under United States federal law if the person in possession does not have the required licensing.{{Cite web |title=18 U.S. Code § 922(o) |url=https://www.law.cornell.edu/uscode/text/18/922 |access-date=2023-05-31 |website=LII / Legal Information Institute |language=en}}