Trigger Mechanisms; A Guide to What's What

[Mad Magyar]

Fast Action Trigger System:
In a nutshell, here's how it works. A round is chambered and the pistol is cocked. The hammer is pushed forward with a thumb and then engage the ambidextrous safety. When the safety is disengaged, the hammer automatically springs into the cocked position for a single-action press of the trigger. There is no longer the heavy double-action 1st shot to contend with. Trigger pull is consistent from first shot to last. These systems are incorporated in the DAEWOO Fast-Action and Para Ordnance Light DA pistols.

[USMCDK]

I never thought a decocker could fail to stop the weapon from firing... wouldn't that mean it's not the decocker though but more likely the safety???

[Shawn Dodson]

DA/SA - Double Action / Single Action. These pistols fire the first round Double Action, and all following shots are fired single action. They generally use a decocking lever to safely lower the hammer, but block contact with the firing pin so the chambered round is not fired.
Caution Decockers can fail, so always point the pistol in a safe direction when decocking. Decocker failures are rare in modern firearms, but do occasionally happen. Some older designs are more prone to failure. If you have any doubt that a decocker is not working properly have the firearm checked by a competent gunsmith or armorer.

This describes a conventional DA pistol. It is DUMBED down terminology for people who don't understand how a DA automatic operates. In MOST cases the hammer can be manually cocked to fire the first shot in SA mode, so they're not really "DA/SA" are they?

DAO with reduced trigger pull - These are the new breed of DA pistols, pioneered by Para Ordnace's "LDA" - Light Double Action. These pistols keep the hammer down, but cycling the slide pre-tentions the main spring / hammer spring. The result is a lighter weight DAO trigger pull, and some also provide for a shorter trigger pull & reset. Some also have the ability to revert back to a full weight DA trigger pull to give a second try if the round does not initially fire - this is known as restrike capability. Beyond Para's LDA, examples are SIG's DAK, H&K's LEM, and some Kel-Tec and Smith & Wesson Pistols. Edit: It has been brought to my attention that the hammer rests in a partially cocked position on the Kel-Tec PF-9, P-32, and P3AT; and possibly a few other pistols as well

Blah, blah, blah, what a bunch of technical marketing gobbledygook! They're DA or DAO. Period. The trigger mechanism performs the same function as DAO - cocking and dropping the hammer. Restrike capability? More marketing nonsense for the uninformed. If the pistol doesn't fire when you press the trigger then you immediately tap, roll & rack to clear the stoppage.

SFA - Striker Fired Action. These pistols use a Striker, basically a hammer & firing pin in one. Most operate similarly to a lightened Double Action. Cycling the slide partially pre-cocks the striker, and the trigger pull finishes cocking the striker before releasing it to fire the round. Some pistols have the striker pre cocked only a small to moderate amount and are much like DAO in a traditional hammer & firing pin pistol. Others almost fully pre-cock the striker and are much like SA in a hammer & firing pin pistol. Others yet have striker mechanisms that are much like DA/SA. Glocks are undoubtedly the best known SFA pistols; others include Springfield Armory XD, Walther P-99 / S&W99, S&W M&P and Sigma, Taurus Millenium, Mil. Pro, 24/7, and CZ 100.

The trigger mechanism is DAO regardless of striker or hammer fired. Pressing the trigger cocks and drops the striker/hammer.

There are three different types of trigger mechanisms:
1) SA
2) DA
3) DAO

Anything else is marketing gimmick or ignorance.

Cheers!

[JohnKSa]

The trigger mechanism performs the same function as DAO - cocking and dropping the hammer.

No, Shawn, it doesn't and you know it doesn't.

Before this new breed of pistol was invented a DA had to trigger cock the hammer against the force of the mainspring. These pistols don't fight the mainspring with the trigger pull because the slide does that work. Therefore the trigger only has to move the hammer without working against the mainspring. It's a different way for the trigger to function and that's why the trigger is so light even though it may seem to operate like a conventional DA from the outside.

Restrike capability? More marketing nonsense for the uninformed. If the pistol doesn't fire when you press the trigger then you immediately tap, roll & rack to clear the stoppage.

Restrike capability is defined correctly in the blurb you quoted. You may not agree with using restrike capability (and you may even have a good point in that regard) but it doesn't change the definition of restrike capability. And while your statement about what to do if a cartridge fails is a position that is held by many, it's not one that is universally held--nor is everyone who advocates the use of restrike capability uninformed.

The trigger mechanism is DAO regardless of striker or hammer fired. Pressing the trigger cocks and drops the striker/hammer.

Well, it is DAO unless it's not. And pressing the trigger cocks and drops the striker/hammer except when it doesn't.

As you already know, not all the guns mentioned in the blurb you quoted have a trigger that will cock the striker/hammer, in fact most of them will not do so. As you know, most of the guns listed require the slide to tension or partially tension the mainspring before the trigger will do anything at all. And you know that's not the way a true DA or DAO behaves because you stated correctly that a DA or DAO has a trigger that cocks and drops the striker hammer.

I suspect that you do actually realize why people might want to understand why a gun that is often called DAO operates more like a SA (externally speaking) in that it requires that the mechanism be cocked by slide action before the trigger will operate.

Anything else is marketing gimmick or ignorance.

Interesting gambit.

So either we agree with you or we're ignorant and/or spouting "technical marketing gobbledygook".

I'm curious--do you "pre-insult" those who disagree with you in an attempt to prevent anyone from posting a differing opinion or do you truly believe that anyone who disagrees with you is automatically mistaken?

[Shawn Dodson]

Before this new breed of pistol was invented a DA had to trigger cock the hammer against the force of the mainspring.

Agreed, the mainspring is indeed under tension. However if the hammer is UNCOCKED then one must press the trigger to cock and drop the hammer (to fire in DA mode). The mechanical shock required to ignite the primer can only be delivered by a fully cocked hammer. Therefore it is simply DA. The amount of trigger pressure may be reduced but the hammer MUST be cocked to deliver adequate mechanical energy, either manually or by operation of the slide or by pressing the trigger - just like any other DA pistol.

Restrike capability is defined correctly in the blurb you quoted.

I described restrike capability as marketing nonsense. That's it. I didn't re-define it. The term "restrike capability" is used in the defense pistol industry and it's presented as an advantage when it's not. If the gun doesn't go bang with the trigger is pressed then the problem is more likely something other than a misfire (empty chamber, failure to feed, unseated magazine, failure to eject). It encourages a user to keep pressing the trigger in the hopes that the gun will eventually fire, instead of taking immediate, positive action to get the gun back up and running. Hence "marketing nonsense."

For example, the M4 carbine doesn't have restrike capability. Neither does the 1911A1.

As you already know, not all the guns mentioned in the blurb you quoted have a trigger that will cock the striker/hammer, in fact most of them will not do so. As you know, most of the guns listed require the slide to tension or partially tension the mainspring before the trigger will do anything at all. And you know that's not the way a true DA or DAO behaves because you stated correctly that a DA or DAO has a trigger that cocks and drops the striker hammer.

This is how Glock describes their trigger mechanism:

"The “Safe Action” system is a partly tensioned firing pin lock, which is moved further back by the trigger bar when the trigger is pulled.

"When the trigger is pulled, 3 safety features are automatically deactivated one after another. When doing so, the trigger bar is deflected downward by the connector and the firing pin is released under full load. When the trigger is released, all three safety features re-engage and the GLOCK pistol is automatically secured again."

Pressing the trigger cocks and drops the striker. Period. The striker obviously cannot be manually or automatically cocked to operate in SA mode.

Operating the slide merely resets the trigger mechanism, which requires tension to maintain positive contact to ensure positive operation. The fact that the striker is "pre-tensioned" does not make it different from any other DAO auto pistol. Press the trigger and it cocks and drops the striker. It does not fire from the "pre-tensioned" position alone otherwise there'd be no need to retract it to "full load" position by pressing the trigger.

(If it were capable of firing from the "pre-tensioned" position alone then it would be an SA mechanism like the 1911A1.)

A Beretta 96SF can be fired, in DA mode, with the hammer in half-cock (i.e., "pre-tensioned"). Should new terminology be invented to describe this ordinary DA trigger function? Install a factory DAO 92D mainspring and one can convert it into a Beretta 96LDA!

How much trigger pressure required is irrelevant - if you press the trigger and the hammer or striker moves backward, then the trigger mechanism is either DA or DAO.

The purpose of marketing is to convince you that product features are unique and superior to competing products.

[JohnKSa]

Agreed, the mainspring is indeed under tension. ... just like any other DA pistol.

I took out all the verbiage in between to demonstrate exactly why it's NOT "just like any other DA pistol."

The term "restrike capability" is used in the defense pistol industry and it's presented as an advantage when it's not. ... Hence "marketing nonsense."

As pointed out earlier, not everyone agrees with you, there are informed people who take a different view. Hence a difference of opinion. There's a difference between saying you wish to present different view (one that is not without merit, by the way) and saying that anyone who disagrees with you is spouting nonsense.

Operating the slide merely resets the trigger mechanism, which requires tension to maintain positive contact to ensure positive operation.

Been through this with you before so I know that you know the truth. I've even posted pictures demonstrating that the slide does NOT merely "reset the trigger mechanism", it does about 50% of the compression of the mainspring while the trigger does what's left. If you would examine a Glock with an open mind you would realize that's FAR more than would be required to "ensure positive operation".

The fact that the striker is "pre-tensioned" does not make it different from any other DAO auto pistol.

It's not just pre-tensioned, it's half-tensioned. And unless all DAO autopistols use the slide to put the hammer at half-cock or half-tension the mainspring then it does make it different from other DAO auto pistols.

But that's just one example out of the entire range of designs you blithely dumped into a single bucket. Some of the designs require the trigger to do all the work of tensioning the striker and don't require the slide to reset the action before the trigger can be pulled again. Others have the slide do almost all the work of tensioning the striker spring. What you're saying is that none of that makes any difference whatsoever.

That's an interesting opinion, but that's all it is. And again, it's certainly not an opinion that is universally shared. Not by any means.

A Beretta 96SF can be fired, in DA mode, with the hammer in half-cock (i.e., "pre-tensioned"). Should new terminology be invented to describe this ordinary DA trigger function? Install a factory DAO 92D mainspring and one can convert it into a Beretta 96LDA!

You would have a point if the gun were actually designed so that the slide action put the hammer in half-cock for each shot and the slide action was required before the trigger would operate. It doesn't work like that so the analogy fails and fails badly.

The purpose of marketing is to convince you that product features are unique and superior to competing products.

Would you say that is something like stating one's opinions as if they are fact?

[Johnny Guest]

Thanks to ugaarguy for his time and effort in writing up the original explanation. Thanks to the others who added their contributions and attempted to clarify the matter farther.

I feel, though, that the more this is thrashed out, the more invested some become in forcing everyone else adopt his own thoughts and nomenclature. Some things are, indeed, absolutes, and some are matters of opinion. I'm shutting down this thread before things become really ugly.

CLOSED

Johnny Guest
THR Staff