In a firearm, the sear is the part of the trigger mechanism that holds the hammer or striker back until the correct amount of pressure has been applied to the trigger; at which point the hammer or striker is released to discharge the weapon. The sear may be a separate part or can be a surface incorporated into the trigger.
The term "sear" is sometimes incorrectly used to describe a complete trigger group. Within a trigger group, any number of sears may exist. For example, a Ruger Blackhawk single action revolver contains one for releasing the hammer. A Ruger Redhawk double/single action revolver contains two, one for single action release and the other for double action release. A Browning BLR contains three sears, all used simultaneously for hammer release. On many select-fire rifles two sears exist, one for semi-automatic fire and the second for fully automatic fire. In such case, the fire select lever disengages one over the other.
Trigger sears are a key component for the trigger pull characteristics. Larger sears create creep while shorter ones produce a crisp pull. Aftermarket trigger companies, such as Bold, Timney, and Jewell, produce products in which sear contact is adjustable for personal preference. When a gunsmith does a "trigger job" to improve the quality and release of a trigger pull, most often the work includes modifying the sear, such as polishing it, lapping, etc.
The sear on many different firearms is often connected to a disconnector, which, after a cycle of semi-automatic fire has proceeded, keeps the hammer in place until the trigger is released and the sear takes over. Many firearms, such as the Colt M1911, use a very generic disconnecting sequence, which uses a notch in the slide of the handgun that the top end of the disconnector returns to after the trigger is released. When the trigger is still under pressure by the firearm operator, the disconnector will not recede to its resting position. On more modern handguns, which include the M1911 Series 80, there is a firing pin block that acts as an internal safety, which is disengaged by the disconnector after the trigger is pulled. But because of the spring tension the disconnector is under by the firing pin block, the weight of the trigger pull is increased significantly. Some weapons are known for having difficult sear-disengagement, like the Browning Hi-Power, while others are prized as excellent.
- Guns by Dudley Pope, 1969, Hamlyn Publishing Group, Ltd. This is an inexpensive large format book with excellent drawings of various firearm mechanisms showing early sears.
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