# Sticky  Trigger Types Defined and Explained.



## VAMarine

For those interested....

There are multiple types of trigger types available for use but most of them are of the following sort:

*Single Action Only*Abbreviated *SAO*

Your two most common types if SAO guns are 1911 pattern semi-automatics and your "Western" revolvers" such as the Colt Single Action Army. A lot of people get confused on this as they mistake _*action type*_ and _*trigger type*_. With both the 1911 and single action revolver, the hammer must be cocked in order for the gun to fire. Pulling the trigger causes one action, that of the hammer to fall and make contact with the firing pin. To confuse you even further, there are some single action only guns that are striker fired as they are fully cocked by the manual cycling of the slide or other operation. Two examples of single action, striker fired guns are the HKP7 family and the Springfield XD (includes XDM) line. There are some that will disagree and say that striker fired guns are not SAO. But looking at the requirement that pulling the trigger facilitates only one action, the release of "X" that initiates the firing sequence, YES they are single action and are even considered SA by the IDPA.

*Double Action* Abbreviated *DA*. 

Most modern revolvers are referred to as double action, despite the fact that they are still capable of being fired in the single action mode, why this is I don't know. Double Action indicates that pulling the trigger caused two actions, 1: the cocking and 2: release of the hammer. One action=two results. Common double action revolvers are the Ruger GP100 and Redhawk 

*Double Action Only*, abbreviated *DAO*.

DAO guns can not be manually cocked, they are cocked and released by trigger manipulation. DAO guns can be revolvers or semi-automatics. Glocks are erroneously referred to as DAO as the trigger must be pulled to fire the gun, THIS IS FALSE. Glocks and many other makes/models are partially cocked, striker fired guns, more on them later.

A DAO gun has the following traits.
1: Is *only* cocked by trigger manipulation and the trigger pull is the same for every shot.
2: In semi-auto guns, the hammer will go back to rest (hammer down behind the slide) after each shot. Remember, the trigger cocks and releases the hammer, not the slide in this case.
3: As the trigger is the driving force to cock and release the hammer, second strike capability is there. If you have questions on second strike capability...try Google, I'm not covering that in this piece. Common DAO guns are the S&W 642 and KelTec P3AT

There are some different types of DAO, such as DAK and LDA from Sig and Para Ordnance respectively, I will cover those in brief at the end.

*Traditional Double Action / Single Action* Abbreviated *TDA or DA/SA*. 

This type of trigger is what is found on the Beretta M9,and other semi-automatic pistols. The first shot can be double action or single action IE one pull of the trigger will cock and release the hammer. If the hammer is manually cocked, the pulling of the trigger will release the hammer. As the M9 is a semi-automatic pistol, the slide will re-cock the hammer after the gun is fired. With a DA/SA type of gun, all subsequent shots will be fired single action until shooting stops and the hammer is de-cocked.

*Partially Cocked Striker Fired* / Striker Fired

Glock, Kahr, some S&W models and others operate on this type of mechanism. What sets these aside from DAO guns is that the cycling of the slide partially cocks the striker and the pulling of the trigger finishes cocking the mechanism and releases the striker to make the gun go bang. Remember what I said before, some striker fired guns fall into different categories.

Now that we go the basics out of the way, we can take a look at some different "sub-types" of triggers. As mentioned previously, out there in the world there are these two strange beasts that are called DAK (Double Action Kellerman) and the LDA (Light Double Action) which are found on so equipped Sigs and Para LDA models.

Per Wikipedia:



> SIG released an altered version of the double-action only (DAO) pistols called the DAK (for Double Action Kellerman, after the designer of the system). The DAK capability is available in 220, 226, 229 and 239 models. When firing the pistol the first trigger pull is 6.5 lbf (compared to 10 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 8.5 lbf (38 N). If the trigger is released all the way forward, this will engage the primary trigger reset and have a trigger pull of 6.5 lbf (29 N). 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. The United States Coast Guard has adopted this firearm as its PDW (Personal Defense Weapon), replacing the older M9 pistol.[9]


As there are two different pull weights?? this is not a conventional DAO.

Para LDA:
Without going into gross detail, the LDA is a super smooth, lightweight trigger. Generally speaking most DAO guns have a heavy pull and no safeties. The Para LDA incorporates the 1911 pattern thumb safety thus allowing for a very light pull but still has the hammer going back to rest after every shot, but if I recall correctly, the LDA has no second strike capability and needs the slide to cycle in order for the trigger to do it's thing in cocking and releasing the hammer.

HK refers to their DAO as LEM (Law Enforcement Modification) which is thought to be another form of lighter double action, but it is really another pre-cocked hammer system, you can read more about it at HK's website

It's a lot of info to take in. Each method has it's advantages and disadvantages. If you'd like to read more on the types of trigger actions on semi-autos, I would definitely recommend checking out Automatics: What Action Type for Me? by Stephen Camp.


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## bruce333

good job

sticky...:smt023


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## VAMarine

bruce333 said:


> good job
> 
> sticky...:smt023


Thanks.


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## hue001t

tag thanx!


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## philiprambo

*Re:*

Really a good post.keep it up.Thanks a lot for sharing.


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## legallyarmed

Thanks, this clears it up for me.


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## Meister

Most people think that trigger types easily fall into double-action or single action. Everyone should take note of this post as it clearly explains that there is much more to it than meets the eye. Great educational piece.


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## BigCityChief

Very nicely done, VAMarine!


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## CW

Why DA revolvers? 

DA allows for quick successive firing. The SA mode allows for a careful more accurate shot mainly because of the significantly lighter trigger pull. 
I suspect this is more of a feature you want in a hunting revolver, but then it also gives you versatility in a defense scenario. A longer shot would do better in SA.

Nice Post VA. The semi auto - SA/DA confused me until I got my 1911a1.


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## SouthernBoy

CW said:


> Why DA revolvers?
> 
> DA allows for quick successive firing. The SA mode allows for a careful more accurate shot mainly because of the significantly lighter trigger pull.
> I suspect this is more of a feature you want in a hunting revolver, but then it also gives you versatility in a defense scenario. A longer shot would do better in SA.
> 
> Nice Post VA. The semi auto - *SA/DA confused me* until I got my 1911a1.


Also called DA/SA, this term is relatively new to the world of pistols and was once referred to as DA. A classic example is the Beretta 92FS. Had you bought this gun 25 years ago, you would have seen Double Action on the box. I suspect the move to the use of DA/SA (or SA/DA) is due to a combination of the advent of DAO pistols and people new to this culture, not knowing or understanding some of the terminologies and being a bit confused.

At any rate, a DA pistol is a DA/SA pistol.


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## Steve M1911A1

There is yet another category, which VAMarine left out:

*Partially Cocked Hammer Fired*
(There's probably a better name for this action, that describes what happens more clearly.)
This system is typified by Kel-Tec's P-3AT and P-32. Although these pistols are hammer-fired, unless their slides have first been racked (by you or by recoil operation), their hammers will move but will not cause a shot to be fired.
To a user, the trigger action seems to be DAO. But in the classic DAO pistol, the gun's hammer snaps down on the firing pin, and will allow second-try primer hits. The two Kel-Tec pistols noted above will not permit this.


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## VAMarine

Yeah... I don't know or care much about KelTecs.


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## Blackhawkman

Everyone knows Glocks are Single Action pistols. fwiw


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## Steve M1911A1

Blackhawkman said:


> Everyone knows Glocks are Single Action pistols. fwiw


Not everyone.
I disagree with your statement.

Although the Glock action does not require that a trigger-pull work from "hammer fully down" (remember: the Glock is striker fired, and has no hammer), neither does the Glock trigger action merely let off the pistol's striker from fully cocked.
The Glock trigger action must first finish cocking the striker, before that striker is let off.

Thus, although the Glock trigger is not strictly a classic double-action mechanism, neither is it strictly a classic single-action mechanism.
The truth is that it is a special case, somewhere in-between.

However, the Glock mechanism is more easily understood, particularly by beginners, if it is seen as a double-action system.
Like the Kel-Tec P-3AT, for instance (although the Kel-Tec has a hammer).


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## siradorta

thanks!


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## Craigh

There are a myriad of various combinations, some not mentioned here. For example, the Ruger LCP II has a fully cocked SA internal hammer but acts more like a DA pistol in use. The Walther PPQ is striker fired, but is also fully cocked after the slide cycles, either by hand or recoil. I suppose it should be called striker fired single action. Again, the pull isn't a typical 1911 type SA. It's more similar in feel to a Glock, but a little lighter pull and a much crisper break. Not sure, but I think the Sig P320 is similar. Because of the so many ways designers have chosen, it's pretty hard to come up with distinct pigeon holes to classify trigger types. People can always point out variants or completely different types.


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## VAMarine

Craigh said:


> There are a myriad of various combinations, some not mentioned here. For example, the Ruger LCP II has a fully cocked SA internal hammer but acts more like a DA pistol in use. The Walther PPQ is striker fired, but is also fully cocked after the slide cycles, either by hand or recoil. I suppose it should be called striker fired single action. Again, the pull isn't a typical 1911 type SA. It's more similar in feel to a Glock, but a little lighter pull and a much crisper break. Not sure, but I think the Sig P320 is similar. Because of the so many ways designers have chosen, it's pretty hard to come up with distinct pigeon holes to classify trigger types. People can always point out variants or completely different types.


The LCPII didn't exist when I wrote this...not that it really matters as its just a single action gun with an enclosed hammer.

The style of operation that the PPQ works in is covered, being a single action striker...

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## Babbalou1956

Do DA/SA pistols have double strike/2nd try capability? If so is it for the first round only or any rounds? I'm not very familiar with these pistols. Never owned or shot one or had much interest in them until lately.


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## Steve M1911A1

Most (and maybe _all_) Traditional Double-Action (TDA) pistols, which you called DA/SA, exhibit second-strike ability.
That is definitely _not_ true of all Double-Action Only (DAO) pistol actions.


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