Handgun - Operating Mechanisms

Operating Mechanisms

Single-action handguns have a trigger whose sole function is to drop a pre-cocked hammer to discharge a cartridge. For revolvers, the popular Colt Peacemaker of Old West fame is typically thought of. Its hammer must be manually cocked for each shot. For auto-loading pistols the Colt 1911 or Browning Hi-Power are typical examples. They must be cocked for the first shot, but subsequent shots are cocked automatically due to the racking of the slide. These types of guns typically have a very light and crisp trigger pull, making for more accurate target shooting.

Traditional double-action handguns have a mechanism that can be either pre-cocked, like the above single-action gun, or can be fired with the gun uncocked. In this case, the gun has an additional mechanism added to the trigger that will cock the gun (and rotate the cylinder in the case of revolvers) as the trigger is pulled. Once the trigger is pulled far enough, the hammer is released and the gun fired. For autoloading pistols the self-loading mechanism will also re-cock the hammer after the first shot is fired so that subsequent shots are fired single-action. For revolvers, each shot is fired with the hammer initially uncocked unless the shooter manually cocked the gun. Popular auto pistols in this category include the Walther P38 and Beretta 92. These guns typically have a longer, heavier trigger pull for the first shot then light, crisp pulls for subsequent shots. Popular revolvers include the Ruger Redhawk and Smith & Wesson Model 29. These have comparatively long, heavy trigger pulls for all shots unless the revolver is manually cocked.

Double-action only handguns do not have the ability to be cocked and is usually evidenced by a lack of either the hammer spur or the entire hammer. A typical autopistol in this category is the Ruger KP93DAO and a typical revolver is the Smith & Wesson Centennial or the Enfield No 2 Mk I*. All pistols in this category have a long, heavy trigger pull for all shots.

Pre-set triggers are only on autoloading pistols. In this case the pistol mechanism is always partially cocked while being carried and during firing. The partially cocked firing pin or striker is not cocked enough to cause an accidental release to discharge a cartridge, adding to the safety of the design, but is cocked enough to remove much of the trigger pull and weight of a purely double-action pistol. These types of pistols do not have external hammers and do not generally have a decock function. Common pistols in the category are the HS2000 (Springfield XD) and the various forms of the extremely popular Glock. The trigger pull of these guns is between double-action and single-action pistols. Pre-set triggers may or may not have a second-strike feature on a dud cartridge.

Some automatic pistol models such as the HK USP Universal Self-loading Pistol (or U.S.P.) come in a variety of mechanism types and can be easily changed by a gunsmith for both left- and right-handed shooters and for different operating mechanism and safety features.

Glock introduced a new "Safe Action" mechanism that is neither a single nor double action. The weapon is never "cocked" in terms of a hammer being "cocked". The partly tensioned firing pin lock is released by pressing the trigger, resulting in the first and subsequent trigger pulls all being the same.