Basic Trigger Definitions (focusing on auto pistols)
1. Single Action (SA): Racking the slide cocks the mechanism from a relatively dead rest. A short-stroke single action trigger (the finest in the industry) releases the mechanism. The classic 1911 pistol epitomizes this style. This system requires a manual safety.
2. Double Action/Single Action (DA/SA): This kind of DA pistol has a dual personality. The first shot is a true long DA action as in definition 3. All the follow-up shots (and the first shot if the hammer is cocked) are short-stroke single action trigger pulls similar to definition 1. The excellent SIG P Series is a good example in this category. This system requires a decocker and/or manual safety so the pistol can be carried safely.
3. Double Action (DA) or Double Action Only (DAO): As the trigger is pulled, a relatively long pull, it performs two actions. The first part of the trigger pull cocks the mechanism from a relatively dead rest. The second part of the trigger pull releases the mechanism to fire the pistol. Note: This is the classic definition of DA, before any interpretations are applied. A good example of this trigger type is the excellent sigpro SP2340 using the DAO SIG trigger kit. This system does NOT require a manual safety or decocker.
4. Safe Action (SA-Glock): This is a Glock trigger system, which does not fit into the above categories cleanly, even though the ATF ruled it a DA pistol approximately twenty years ago. Internally, the firing pin mechanism is half cocked when the slide is racked. Quoting directly from the Glock Owner's Manual: "Cock pistol by pulling slide back to its rearmost position and let it run forward. The pistol is now half-cocked" - end of quote. Therefore, the Glock is actually a HYBRID 1/2 SA & 1/2 DA trigger system. Is the glass half full, half empty, or both? Do we round up from 1/2 SA/DA to full DA? Yet externally, the Glock has the look and feel of an excellent, "safe double action trigger system with appropriate built in safeties" for the end user. This trigger system does NOT require a manual safety or decocker.
5. Ultra Safety Assurance (USA-XD): This is a Springfield XD trigger system, which does not fit into the above categories cleanly. Internally, it is classified as a single action. Yet externally, the XD operates very differently than typical pistols in the Single Action category that use short-stroke single action triggers and require a manual safety of some kind (see definition 1). That's because the XD, just like the Glock, has the look and feel of an excellent, "safe double action trigger system with appropriate built in safeties" for the end user. This system does NOT require a manual safety or decocker.
6. DA-Like (DAL), or Bio-Mechanical DA (BMDA): This new definition is required in order to honestly appraise some of the newer pistols that cannot cleanly fit into the classic SA, DA/DAO, DA/SA trigger system definitions. Note: Nothing is sacred about these three classic standard trigger systems (definitions 1, 2, & 3). As pistols evolved, these pistol trigger definitions were simply created as needed in order to accurately describe the overall pistol functionality. But some of the newer style pistols operate ergonomically (biotechnology) as Double Action pistols, although internally they do not fit the classic DAO definition 3. Ayoob calls this new trigger category a bio-mechanical DA trigger since the trigger feels like a regular DAO Trigger system to the end user. I prefer the shorter definition of simply "DA-like" or "Striker Fired Action" if appropriate. Some pistols that fit into this category: Glock, Walther, Springfield XD, and the Steyr M series pistols, to name a few.
http://www.handguninfo.com/Archive/www.Pete-357.com/xddasa.htm
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Слишком растянуто и воды много. Откуда между одинарным (SA) и двойным (DA) действием взялось 6 вариаций? Есть только эти две базовые позиции - остальное компромисс/комбинации между ними.