Descriptions of semi autos

[roughcreek]

These are sometimes confusing for me.
Can I make the following generalizations:

1. Striker fired semi autos are are all SAO (single action only) Understand there
is some rearward movement of the striker when the trigger is pulled.
2. DAO (double action only) semi autos have a hammer.
3. DA/SA have a hammer and a decocker.

It is surprising to me but sometimes when I pick up a gun at a show
and ask what the action is, they don't know. So that is no help.

Thanks for your input.

Roughcreek

 

[pblanc]

Some striker-fired action (SFA) pistols are designated SAO and some are designated DAO depending on how completely the striker is tensioned by the slide cycling. I agree that most SFA pistols trigger actions more closely resemble the single action trigger of a traditional double action (TDA) pistol or double action revolver than they do the double action trigger of the same, or a DAO pistol.

Then of course, there are single action (SA) or SAO pistols which generally have a frame-mounted safety (no decocker).

Not all TDA pistols have a decocker lever. Many have a decocker/safety lever. I believe the earlier Taurus PT92s had only a frame mounted safety without a decocker. The newer ones have a three position safety/decocker lever.

 

[MaterDei]

Took a while for you to make your first post.

1. Striker fired semi autos are are all SAO (single action only) Understand there is some rearward movement of the striker when the trigger is pulled.

- Striker fired vs hammer fired pistols don't align consistently with the type of action that they have. Most striker fired pistols are in fact DAO, not SAO. With a SAO action, pulling the trigger simply releases the sear allowing for the striker/hammer to fall, there is no other action other than possibly deactivating a trigger activated safety.

2. DAO (double action only) semi autos have a hammer.

- Based upon my response on 1, this statement is sometimes true and sometimes false. Most semi-autos with a hammer are SA/DA but I am sure there must be a DAO hammer based semi, I just can't recall one at the moment.

3. DA/SA have a hammer and a decocker.

- Many do, yes. Many have a safety with no decocker, e.g. CZ 75B. Some have a decocker and no manual safety, e.g. CZ 75BD and some have both, e.g. HK USP.

 

[ATLDave]

3. DA/SA have a hammer and a decocker.

As others have noted, that's an incorrect statement. Plenty of DA/SA guns have a traditional safety that does NOT drop/lower the hammer.

 

[Sam1911]

1. Striker fired semi autos are are all SAO (single action only) Understand there is some rearward movement of the striker when the trigger is pulled.

No. Some partially cock the striker before releasing it, some don't. (Or don't enough to talk about.)

There are even some striker-fired autos with a "second strike" facility, by which if the striker drops on a dud primer, pulling the trigger again will fully cock and release the striker.

2. DAO (double action only) semi autos have a hammer.

Not necessarily.

3. DA/SA have a hammer and a decocker.

Not always.
Some have a decocker, some have a safety. Some have a safety AND a decocker.

 

[Deanimator]

3. DA/SA have a hammer and a decocker.

There are a number which do not, to include:

• CZ75B
• Bernardelli P018
• Taurus P9x series

 

[bannockburn]

roughcreek

Some DA/SA pistols, like the Taurus Model 92, have a frame mounted three position safety lever from which you can 1) decock the pistol by safely lowering the hammer so it can be fired in the DA mode; this is done by pushing the lever down and letting it return to the OFF position), 2) with the hammer cocked you can put the safety on by pushing the lever upward, making the pistol safe to carry in the SA mode and 3) you can also apply the safety upward while in the DA mode.

 

[Telekinesis]

Striker fired and hammer fired dont always align with SAO, DAO, or DA/SA.

Striker fired guns like the Springfield XD are SAO, the Glocks are partially (but not fully) cocked, I believe Khars are traditional DAO, and the Walther P99 is a true striker fired DA/SA.

Hammer fired guns can be SAO like a 1911, DA/SA like a Sig 226, partially cocked (similar to glock's action but with a hammer) like a HK LEM trigger, or true DAO like found on some other HKs. (The HK USP is actually an interesting gun when this topic comes up because one gun can be fitted with either DA/SA, DAO, or LEM trigger groups by an armorer).

In short, you can't make generalizations about what type of trigger a gun has just by whether it is hammer fired or striker fired.

 

[pblanc]

The SIG P250, Beretta 92D and Beretta Cougar D models are a few examples of hammer-fired, double-action only semi-automatic pistols.

 

[CZ9shooter]

I personally give striker fired handguns their own category.

DA/SA
DA only
SA only
And striker fired.

Now I guess a manufacturer could produce a striker fired gun with a short, light, truely SA trigger, with very little creep and behaves much like a traditonal SA pistol. Such a design would certainly require a manual saftey. If that were the case I might group it into the SA category. Maybe such a weapon exists, but I have yet to find it.

 

[jmr40]

Glock calls their trigger "Safe Action". Most classify it as DAO, same with the Smith M&P. XD's are SAO. The difference in the real world is pretty small, but that distinction is what keeps most LE agencies from considering XD's as most have reguations requiring DAO or DA/SA pistols.

 

[9mmepiphany]

I think others have offered examples that contradic your statements, except for #2

2. DAO (double action only) semi autos have a hammer.

The Walther P99 and the Kahr line of pistol are DAO and neither has a hammer. If you go back to the first mass produced polymer framed semi-auto...the H&K VZ 70...it was striker fired and also DAO

 

[Walt Sherrill]

In recent years, the definition of what SINGLE and DOUBLE ACTION mean seems to have been thrown askew by the rise of striker-fired weapons. But the Luger, one of the earliest mass-produced striker-fired guns was considered a Singe Action (SA) weapon, so I'm not sure that whether a hammer- or striker-fired is really all that important when using these terms. As I first learned the terms SINGLE ACTION or DOUBLE ACTION, they described the role the trigger played in making the gun work. I'll continue using that approach here, but others may disagree.

Here's my take on the topic, and I think the following addresses the many different options all in one place. I may have overlooked a variation or two.

• Single Action (SA) guns use either slide movement (when loading the chamber the first time) or hand cocking the hammer to fully tension the striker or hammer spring and make the gun ready for action. Pulling the trigger releases the spring and slide movement readies the weapon for subsequent shots. Single-action weapons can be both hammer-fired or striker-fired.
  
  
• Double Acton Only (DAO) guns have triggers that both fully charge (tension) the hammer or striker spring and release it in one motion. This is seen in both hammer-fired and striker-fired guns. There are a many DAO revolvers, DAO semi-autos, and a few striker fired DAO guns. DAO guns do not have safeties or decockers.
  
  
• Double Action/Single Action (DA/SA) guns start from DA mode, with the trigger charging the striker or hammer spring and releasing it (just like a DAO gun). With following shots, the slide charges the hammer or striker spring and the gun functions just like a SA weapon, in that the trigger ONLY releases the hammer or striker in those subsequent shots, when the shooter is ready.
  
  Most DA/SA guns (like SIG hammer-fired guns and a few striker-fired guns (like some Walther models), have decockers.
  
  A few hammer-fired DA/SA (like some CZ or Witness models) have safeties rather than decockers. The safeties allow the shooter to start from SA mode if the choose, just like a SA gun. with the hammer cocked and a safety on ("cocked & locked") or start from hammer down as they would with a DA gun.
  
  A few other DA/SA guns have multi-function levers that allow the shooter to decock a cocked hammer or start from cocked and locked (and SA mode) with the safety engaged.
  
  
• Modified DA (MDA) guns are those which use slide movement to partially (sometimes nearly fully) charge the striker or hammer spring, and the trigger completes the "charging" process and releases the spring. Glocks work like this, as do some versions of the hammer-fired S&W 3rd Gen semi-autos.
  
  Some of the MDA guns have safeties. The Kel-Tec PF9, the Ruger LC9, and some of the 3rd Gen S&Ws (called Hybrid Double Actions in a following post) fall into this MDA cartegory.
  
  In many cases, the triggers in the MDA, DA/SA and even SA guns can feel very similar to the shooter using the weapon. Only the DAO models are quite different.

 

[roughcreek]

Holy Cow!!!! What a selection. I guess I'll stick with the 1911 for now.
Maybe watch at the range and see if I can try a few different systems used by
other shooters..
1911 getting a little heavy as I grow older and looking for something similar
but lighter..Thanks for all the replies. Very informative. Appreciate it.

Roughcreek

 

[MedWheeler]

The coroner's report on the Zimmerman case labels the Kel-Tec PF9 used as a "hybrid double-action." It's a hammer-fired, partially-cocked weapon. Pulling the trigger completes the hammer's rearward travel, then releases it.

If the hammer is fully at rest (only way to get it there is to dry-fire it, or have it fail to fire), pulling the trigger will not cycle it again; it must be returned to the partially-cocked position first.

Now, Kel-Tec's other 9mm pistol, the P11, has a hammer that is always at rest unless it's actively being cycled by the trigger. It's a "true" DAO.

Just an example of some of the differences out there...

 

[Zerodefect]

Glock. It's the only thing I've taken to since being a 1911 guy.

I consider striker fired pistols closer to a DAO trigger than single action. The Glock pulls the striker rearward before tripping, and sling shoots the striker forward into the primer.

1911's are true single action.

SA=1911, CZ75sa
DAO=Kahr, S&W J-frames, Ruger LCR, Ruger LCP, Keltec.
Striker fired DAO= Glock, M&P, XD
DA/SA= M9, CZ75b, Ruger P95

 

[mgmorden]

Separate striker and hammer from the action type.

There are 4 general types:

1. Single Action (SA) - the ignition mechanism is fully cocked each time.
2. Double Action/SingleAction (DA/SA). The ignition mechanism can start from a completely decocked state and do a double-action pull, and subsequent shots are single-action. MOST of these will provided a decocker to move the gun from cocked to decocked, but not all.
3. Double Action Only (DAO) - Every time the gun cycles its left in a fully decocked state.
4. Partially tensioned (no good acronym for it ) - the cycling of the action PARTIALLY cocks the ignition device but upon pulling the trigger it finishes cocking it the rest of the way and then drops it. Typically these actions have trigger pulls slightly heavily than SA guns but much lower than DAO. If the gun is fully decocked (ie, a dud round) it generally cannot be fired again without cycling the slide.

Then, there is the ignition mechanism:

1. Hammer
2. Striker

Now, the VAST majority of striker fired guns fall into the partially tensioned category, but not all. Most Taurus striker fired guns for example are striker fired but are DA/SA. The Canik TP9 is as well, but the TP-9 SA is an SA gun. Walther's P99 comes with all sorts of different action types that can fit nearly any of the above.

On the flip side, hammer fired guns are USUALLY SA, DA/SA, or DAO, but there are a few that are pre-tensioned. The Walther PPX for example and the Beretta PX4 'C' model.