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Any discussion about handgun actions and triggers is not as simple as just listing a few universally-accepted types and describing their evident characteristics. I am sad to say this and don’t want to make this more complex than it is, especially for new shooters, but there are several key factors in gun actions to think about that may have life-altering consequences. The “action” of a handgun refers to the mechanical relationships between the trigger and the hammer. No matter what action, the trigger’s most basic function is to release the hammer or striker. But depending on the action type, the trigger may cock the hammer/striker, deactivate passive safeties, rotate the revolver’s cylinder, and complete several other functions. Pressing the trigger with some actions may both cock and release the hammer, while with others only one result occurs. All types have advantages and disadvantages. There are strong opinions about all trigger actions, so do your own research for your own personal decision. What type of action do you want in your handgun? Why?
Several shooters don’t even think about their trigger type or action when purchasing or using their handgun nor when defining what they want up front when buying one. Consider: What are the common types of handgun triggers and which one[s] is[are] best for you and your purpose[s]? How do you compare one type of trigger or action to another? What are the characteristics of each trigger type and action? Can you be more accurate with one type of trigger over another? Can you fire one trigger/action type faster than another to help you confront bad guys/gals and for multiple attackers? Now these questions are not meant to be frightening or scare you as a new shooter or someone concerned about self defense. But there are many trigger and action factors at play when shooting which directly affect shot placement, follow-up shots, the amount of force required for the shot, movement, and outcomes. Trigger control is one of the most crucial shooting fundamentals and I believe THE most important one, although several are very important. You must know your gun’s trigger and action and how to properly manipulate and control it; familiarity and practice are paramount. You should know that some shooters even disagree on the trigger mechanisms, features, pros and cons, and benefits. The basic information that follows about trigger actions is meant to be introductory for new shooters and a refresher review for experienced shooters, based on my very basic understanding. Certainly, be open to what others believe about trigger types and benefits, do your own research, and then try it before you make your own decisions. Each type has its own merits. This information is meant to help you understand the type and characteristics of the trigger you have on your present gun and to help you when generally operating it and purchasing future guns.
There are 5 common types of trigger mechanisms or actions on handguns. I will refer to them as types of triggers. It is important to know the type of action for your handgun because it involves whether or not a hammer must be cocked for the gun to first fire, whether a firing pin or striker bar operates, how many actions must occur for the gun to fire, whether or not the gun is only cocked by trigger manipulation, what trigger press weight is necessary for the gun to fire, whether the slide must be cycled to cock the gun, and other things. So you see that the type of trigger affects you the shooter in many ways, the least of which is not your quick follow-up shots, the amount of movement, and the necessary force to press the trigger for accuracy to defend your life. While the definition of the various actions can be specified, as I mentioned there is disagreement and debate about the type of actions that some guns have and their operations. But, here are my 5 trigger actions.
Common Trigger Action Types
The 5 common trigger actions or types are:
1) Single Action Only (SAO);
2) Double Action (DA);
3) Double Action Only (DAO);
4) Double Action/Single Action (DA/SA); and
5) Striker-Fired or Partially Cocked Striker (SF).
Single Action Only (SAO)
A SAO trigger performs the single (only) action of releasing the hammer or striker to fire the gun each time the trigger is pressed. If the hammer is not cocked on a SAO gun like a 1911, pressing the trigger will result in no shot being fired. Generally, the SAO is the simplest action and the shortest, lightest, and smoothest press. The press is also consistent from shot to shot, so minimal adjustments in technique are needed for proper accuracy. A major advantage of most SAO pistols is that, when cocked, the firing mechanism can be released and fired with a very short press of the trigger, usually less than 1/4″, as well as a soft press (near 4 pounds or so.) Less movement from exerting less force on the trigger usually means a more accurate shot. On a SAO pistol, the hammer will be cocked and the gun ready to fire by chambering a round, so often an external safety is used. Many prefer to carry a SAO “cocked and locked” with a round in the chamber and the safety on. Proper training and practice are important for this carry technique and new shooters should be very cautious and deliberate in this decision. Examples of the SAO pistol include the Colt 1911 Government Model, the Browning P-35 Hi-Power, the German P-08 Luger, the Springfield 1911 EMP, the Sig 238, Beretta Neos, Ruger Mark III, and the Russian Tokarev TT33. Many early firearms of single action design are revolvers (like the Colt Single-Action Army [Peacemaker]-introduced in1873-think Buffalo Bill Cody, Theodore Roosevelt & Gen. George Patton), but some semi-automatic pistols, such as the Colt 1911, must be manually cocked before the first round may be fired and is automatically cocked for successive shots, are also SAO. Almost all rifles and shotguns use this type of trigger. For SAO pistols then, to chamber the first round you rack the slide and then the movement of the slide ejects the empty case and automatically chambers the next round, after firing. While SAO pistols require that the hammer or striker be cocked before the first round can be fired, most designs cock the hammer or striker as part of the loading process (i.e. the act of inserting the magazine and operating the slide to chamber the first round also cocks the hammer or striker into the ready-to-fire position.) Again, once the first round is fired, the automatic slide movement (recoil) cocks the hammer or striker for each subsequent shot. Then once cocked, the pistol can be fired by pulling the trigger once for each shot until the magazine is empty.
An Ongoing Debate: Note that some say that striker-fired (SF) guns are really SAO, as they are fully cocked by the manual cyclng of the slide or other operation. Others disagree and believe that SF guns are not SAO and are DAO. In actuality, there are different types of SF guns and they are pseudo-SAO or pseudo-DAO in nature. There are some SF guns that are more SAO, like the Springfield Armory XD with no hammer and fires when you press the trigger. (Some debate this still.) Then there are Glock SF guns which are more like pseudo-DAO with a pre-set, partially-cocked function. What sets these apart from DAO guns is that the cycling of the slide partially cocks the striker with its built-in spring-loaded firing pin and then the pulling of the trigger then finishes cocking the striker bar and releases it to strike the primer and ignite the cartridge to make the gun go bang. Keep in mind the above SAO definition that requires the trigger to be pressed to perform only one action, the release of the hammer or striker to make the gun go bang. In a pure SF system, such as with all Glocks, Smith & Wesson M&Ps, Springfield XDs, and Ruger SR9s and SR9Cs, there is no external hammer and no means to de-cock the gun. They are cocked by racking the slide and the usual way to de-cock is to press the trigger. There are even some pseudo DA-SA SF guns, like the S&W SW99 pistol. I believe that technically speaking that SF guns are neither purely DAO nor purely SAO guns, but in their own category of SF. Some SF guns are single action (e.g. my Springfield XD-9 Mod 2), since racking the slide cocks the striker and then the trigger releases it to fire. Other SF guns are double action (or double-action-only), since racking the slide has no effect on the action and the trigger will cock and release the striker. Many striker-fired guns are sort of a hybrid between single and double-action. In those, the slide does part of the work of cocking the striker, but the trigger then completes the cocking action and then releases the striker to fire the gun (e.g. Glock 17 and 19). In those guns, both slide action and trigger action are required to fire the gun. Note that the International Defensive Pistol Association (IDPA) has debated the SF issue for some time. The 2015 IDPA Rule Book, Section 220.127.116.11, specifies that DA, DAO, and SF semi-automatic firearms now compete in SSP, CCP, or BUG divisions with SAO guns competing in a separate division, like in ESP, CDP, depending upon size and cartridge used, etc. Previously with IDPA, the Springfield XDm was categorized as SAO. Two examples of single action, SF guns are the HKP7 family and the Springfield XD (includes XDm) line.
Click next for Double Action triggers.
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Double Action (DA)
DA indicates that pressing the trigger causes two (double) actions at the same time: (1) cocking and (2) releasing the hammer. DA triggers provide the ability to fire the gun whether the hammer is cocked or uncocked. This feature has proven attractive for police, military, and self-defense shooters. One disadvantage (to some and not to others) of any DA trigger is the extra length the trigger must be pressed and the extra weight required to overcome the spring tension of the hammer (or striker.) Recognize that most modern revolvers are referred to as DA despite that they are capable of being fired in the single action mode. If you manually cock the hammer with your thumb then press the trigger, that is SA. Common DA revolvers include the Colt Python .357 Magnum, S&W Model 29 .44 Magnum, and the Ruger SP101 .357 Magnum, Ruger LCR .38 special, and Ruger Redhawk in .45 auto. Some DA pistols can be manually-cocked with the external hammer and then pulling the trigger alone fires the gun. These DA guns, sometimes referred to as DA/SA, can also be fired in SA mode, while DAO guns do not allow for SAO firing and have no accessible hammer spur. DA triggers are significantly heavier and longer than SAO because they have to both pull the hammer back and release it in the same step.
Double Action Only (DAO)
DAO guns cannot be fired in SAO mode. DAO guns cannot be manually cocked, since the hammer is only cocked and released by trigger manipulation. The hammer will not be automatically cocked after a shot is fired. It returns to a decocked position after each shot. DAO revolvers are seemingly hammerless, so they cannot be manually cocked and shot in single action. Some call this a “shrouded” hammer because the hammer is internally hidden by metal to prevent an exposed external hammer from snagging on clothing during a draw. Note that the hammer will still function if the gun is fired from inside a coat pocket, for example. Also recognize that some enclosed hammers can be cocked, but it is difficult because you can barely get your thumb on it to cock it.
So trigger control is especially very important with a DAO. The length and force of the trigger press is crucial and trigger control deviations and erratic movements tend to amplify errors. I believe that frequent practice is very important to master a DAO press for accuracy. The trigger press is usually consistent among these guns, but the press is usually harder and longer than striker-fired or SAO guns. Common press-force range is 5.5 to 7 pounds for pistols and 8 to12 pounds for revolvers. DAO guns can be revolvers or semi-automatic pistols. In DAO pistols, the hammer (usually internal, but can be external) will go back to rest behind the slide after each shot. So, the trigger cocks and releases the hammer, not the slide. Since the trigger cocks and releases the hammer, second strike capability is there. In a DAO pistol, you still have to rack the slide to chamber the first round, but racking the slide does not cock the hammer (or striker.) Racking the slide loads the pistol, but it remains uncocked. Pressing the trigger first cocks the hammer, then releases it… two (double) actions. Subsequent shots are also double action. The Walther P99 is just one example of a DAO pistol, while the Ruger LCR .38 special is an example of the DAO revolver.
Why would a shooter want a heavier and longer trigger stroke of a DAO pistol? One advantage is the different distance the hammer falls in DAO versus SAO mode. Single actions generally require the hammer to be much further away from the primer than DAO firearms. The shorter the distance provided by DAO decreases the time and hammer motion that can disturb the sight picture, affecting accuracy. DAO guns resolve some DA/SA concerns by making every shot a DA shot. Since there is no difference in press weights, training and practice are simplified. Also, some claim that negligent discharges are mitigated because of the heavier trigger press and some law enforcement departments require a DAO gun or certain heavier triggers. So safety is an issue. Since DAO pistols cannot be manually cocked, they help minimize dangerous situations such as holding a cocked gun on another. This is one reason DAO guns are popular with law enforcement, but many say safety is a training matter and a learned behavior from proper practice. Remember, your brain is your best safety.
Click next for Double Action/Single Action, Striker-Fired or Partially Cocked Striker.
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Double Action/Single Action (DA/SA)
This type of trigger is what is found on the Beretta M9, the Sig 226 and 232, the Taurus, the Beretta 92 and Px4 Storm, and other semi-automatic DA/SA pistols. The first shot can be double action or single action, depending on if the trigger is pressed initially for double action or if the hammer is manually cocked back with the thumb for single action, but one press of the trigger does cock and release the hammer if it is not cocked manually. If the hammer is manually cocked, the pressing of the trigger will release the hammer. With the M9, for example, as a semi-automatic DA/SA pistol, the slide will re-cock the hammer after the gun is fired. With a DA/SA type of gun, all subsequent shots after the first DA press will be fired single action until shooting stops and the hammer is de-cocked. A DA/SA gun is always ready to fire as soon as the trigger is pressed with no need to disengage a safety. A concern (not insurmountable) that I have with my DA/SA guns is the hard first press of somewhere between 8-12 pounds (DA), but you can train to overcome it. My biggest concern with my DA/SA pistols is making the transition from the first long and hard press in double action to the second shot which is the short and soft single action press (ranges from 4 to 6 pounds or so.) There is a notable difference that we sometimes do not focus on in the “heat of battle.” I learned this in one of my first IDPA matches. Some even call the first DA shot a throwaway because there is so much movement with the first hard press that misses or off bullseye hits regularly occur… unless you practice and train for it. So I have found for me that my DA/SA pistols are harder to shoot well compared to my SAO, DAO, and striker-fired guns. I guess I just don’t want to dedicate extensive practice time with my DA/SA pistols, because I enjoy my others so much more. A personal preference thing. DA/SA guns have versatile mechanisms, are very shootable with proper instruction and training, and are great for teaching and learning trigger control. With the DA/SA gun, you must remember to safely decock it when you are not ready to fire. Holstering without decocking it first is very dangerous. I decock whenever my gun comes off target with no immediately obvious target to engage next. SAFETY FIRST. This is a step not necessary for SAO/DAO/Striker-Fired guns.
Striker Fired/Partially Cocked (SF)
SF guns strictly speaking are neither DAO nor SAO trigger mechanisms. They are striker fired, with their own system, trigger safeties and striker blocks, etc. For me, they offer a good balance of press weight, trigger travel, safety, and consistency. In SF pistols, the trigger engages the firing pin (which is part of and at the end of the striker) directly through a linkage called a striker trigger bar rather than by engaging and releasing a hammer to fall against the firing pin, as in hammer-fired guns. So, SF guns do not have a hammer or a separate firing pin. As the trigger is pulled the striker bar is drawn reward and eventually released. The end of the striker acts as a firing pin and strikes the primer, firing the gun. There is a sub-category of SF pistols in which the striker bar is left in a partially retracted position, after each shot, in order to make the trigger pull lighter. Glocks, M&Ps and XDs are in this category. The slide does about half the work of cocking the striker and then the trigger completes the other half of the cocking action and then releases the striker. Generally per my armorer friends, Glock’s striker must be retracted further than those of the M&P and XD in order to be released to come forward to fire a cartridge.
Another sub-category of SF pistols releases all striker energy returning the striker to a fully at rest position, so that it is not under spring tension. So many SF pistols are “pre-cocked” by slide action. The cocking can be partial or fully cocked, depending on the design. My layman, non-gunsmith understanding is that pressing the trigger simply releases the striker if the SAO SF type OR finishes cocking and releases the striker bar if the DAO type. This latter type of DAO SF is what Glock calls its Safe Action. But recognize that SF guns are not a true DAO. Some say they really operate as a SAO because the slide must be moved backward in order to activate the striker and the shooter cannot press the trigger cocking and dropping the hammer as a pure DA would. Most SF guns (not all) lack a manual safety, so recognize that if you do not press the trigger, the gun will not fire. For example, the Ruger LC9s and variants of the M&P do have an external, manual safety. A primary SF disadvantage is that pressing the trigger a second time after a failure to fire will not re-strike the primer. Usually not an issue since loading the gun requires that the slide be retracted to preset the striker. The usual way to decock is to pull the trigger on typical SFs. Most SF pistols cannot be decocked, e.g. Glocks. To reduce tension, remove the magazine, check the chamber to ensure it is empty, and cautiously and safely press the trigger. Clearing a malfunction usually involves retracting the slide following our Tap, Rotate, Rack, Assess, Bang drill anyway. Examples of SF guns include: Sig 320 series; S&W M&P series; Springfield XD, XDm, XDs series; Ruger SR series & LC9s; Glocks; H&K VP9; FN FNS-9; Walther PPQ M2 (SAO) & P99 (DA/SA); Beretta APX; Kahr CT9. The H&K P7 and Walther PPQ series to me fit the SAO SF model. Note the Walther P99AS is a SF DA/SA model and the PPQ M2 is more like a SAO SF.
SF advantages include no external hammer to snag on things and consistent trigger press with same weight through all presses. Some consider the lack of an external safety on most SFs to be an advantage because fewer steps are involved, since the manual safety does not have to be disengaged. Others believe that there is a safety risk to carry a pistol without external safeties. Some desire the traditional hammer-fired guns, while others prefer the SF guns. These are very hotly-debated issues. What do you think?
Aside from understanding the 5 basic types of triggers, recognize there are some sub-type variants of actions and some unique triggers that exist. Variations like the Para LDA (Light Double Action), H&K LEM (Law Enforcement Modification), Sig Sauer DAK (Double Action Kellerman), etc. For example, the Sig DAK trigger system was developed by Sig Sauer engineers with the goal of having a safe, reliable and consistent 6.5 pound double-action-only (DAO) trigger press with double-strike capability and a short reset. When firing a DAK pistol, the first trigger pull is about 6.5 pounds of force (compared to about 12 pounds for the standard DAO). After the pistol fires and the trigger is released forward the trigger has an intermediate reset point that is approximately halfway to the trigger at rest position. The trigger pull from this intermediate reset point is heavier at about 8.5 pounds. If the trigger is released all the way forward, this will engage the primary trigger reset and have a trigger pull of 6.5 pounds. To engage the intermediate reset the trigger must be held to the rear while the slide is cycled, either manually or by the recoil of a round being fired. With the H&K LEM DAO trigger variant (e.g. my H&K P30 LEM, Light Version 1), you have a short, light, and consistent trigger press (about 4.5 pounds), after a long initial trigger travel but with a short reset and the same light trigger press each time. I love mine, but you have to practice and get use to it. Because DAK, LDA, and LEM triggers move all the way forward between shots IF you let them, you never run the risk of losing contact with the trigger between shots. To me this means much less chance of slapping the trigger when shooting fast. The LEM short reset and consistent light single-action-type press is impressive for me, IF I can get use to the longer trigger travel up front and taking up the slack. These are a few action variations, but there are others.
I hope this information has helped you better understand trigger actions and the many variations, so you can try them for yourself and make an optimal purchase decision and better operate your handguns.
Photos by author.
This personal opinion article is meant for general information & educational purposes only and the author strongly recommends that you seek counsel from an attorney in your state or jurisdiction for legal advice and your own personal certified weapons trainer for proper guidance about shooting & using YOUR firearms, self-defense, stand your ground law, and concealed carry. This is not legal advice and not legal opinions. It should not be relied upon as accurate for all shooters & the author assumes no responsibility for anyone’s use of the information and shall not be liable for any improper or incorrect use of the information or any damages or injuries incurred whatsoever. Safety First!
© 2015 Col Benjamin Findley. All Rights Reserved. This article may not be reprinted or reproduced in whole or in part by mechanical means, photocopying, electronic reproduction, scanning, or any other means without prior written permission. For copyright information, contact Col Ben Findley at ColBFF@gmail.com.