Trigger safety

In firearms, a safety or safety catch is a mechanism used to help prevent the accidental discharge of a firearm, helping to ensure safer handling.

Safeties can generally be divided into subtypes such as internal safeties (which typically do not receive input from the user) and external safeties (which typically allow the user to give input, for example, toggling a lever from "on" to "off" or something similar). Sometimes these are called "passive" and "active" safeties (or "automatic" and "manual"), respectively.

Firearms with the ability to allow the user to select various fire modes may have separate switches for safety and for mode selection (e.g. Thompson submachine gun) or may have the safety integrated with the mode selector as a fire selector with positions from safe to semi-automatic to full-automatic fire (e.g. M16).

Some firearms manufactured after the late 1990s include mandatory integral locking mechanisms that must be deactivated by a unique key before the gun can be fired. These integral locking mechanisms are intended as child-safety devices during unattended storage of the firearm—not as safety mechanisms while carrying. Other devices in this category are trigger locks, bore locks, and gun safes.

The most common form of safety mechanism is a switch, button or lever that, when set to the "safe" position, prevents the firing of a firearm. Manual safeties are as varied as the designs of firearms themselves, but the two most common mechanisms are a block or latch that prevents the trigger and/or firing mechanism from moving, and a device that disconnects the trigger from the firing mechanism of the firearm. Other designs may block the hammer or striker from forward movement or act as a block to prevent them from contacting the firing pin. These are the oldest forms of "active" safety mechanism and are widely used; however, many "double-action" firearms such as revolvers do not have manual safeties as the longer, harder trigger pull to cock and fire double-action provides adequate trigger safety, while keeping the firearm in a more ready state.

A grip safety is a lever or other device situated on the grip of a firearm which must be actuated by the operator's hand, as a natural consequence of holding the firearm in a firing position, in order for the firearm to fire. It is usually similar to a manual safety in its function, but is momentary; the safety is deactivated only while the shooter maintains their hold on the grip, and is reactivated immediately once the shooter releases it. The M1911 design is a popular example of a handgun with a grip safety. The Uzi submachine gun is another example of a firearm with a grip safety.

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