Friday, April 07, 2006

What do single-action and double-action mean?

by B.B. Pelletier

This is for the call desk at Pyramyd Air, where they say they get asked this question all the time. When I use either term in print, I wonder if everyone understands it, so I'd like to explain both today.

Single-action came first
The first type of trigger was the single-action style. All the trigger does is release the hammer or striker. When the gun is cocked, the trigger can then release the hammer or striker so it can travel to the end of its path, as defined by the design of the gun. If it's a flintlock, the hammer carries the flint to strike the hardened frizzen and cause sparks. As the hammer continues to fall, it directs the sparks into the pan to ignite the gunpowder that flashes through the touchhole to set off the main charge in the barrel.

The poster boy of single-action revolvers is the Colt Single-Action Army. One of its nicknames was "Old Thumbbuster."

Colt's ever-popular M1911A1 pistol is also a single-action. The hammer must be cocked before the trigger will work. The action of the slide coming back in recoil (blowback) cocks the hammer for the next shot. But, for the first shot, the hammer is cocked manually.

If the hammer is on a percussion gun, it falls on a percussion cap with force to explode it from the shock. If the hammer is on a firearm that uses cartridges, it either impacts a primer directly and causes an explosion that ignites the main charge of gunpowder, or it strikes a firing pin that does the same thing. The single-action mechanism does just one thing: it releases a hammer or striker to do its job.

What is a striker?
A striker is a heavy firing pin that acts as both a firing pin and a hammer. It has enough mass to set off a primer, but it doesn't look like a hammer. In fact, most strikers look like fat firing pins. The firing pins on most bolt-action rifles are actually either strikers by themselves, or they are attached to extra mass and then function as strikers. So it is possible for a single-action gun not to have a hammer and still be single-action. The way to know whether it's a single-action is to understand what the trigger does. If it just releases the hammer (or striker), it's a single-action.

A striker-fired pistol
It didn't take long before the autoloading pistol did away with the hammer for the more compact striker. Hugo Borchardt invented an autoloader in 1893 that eventually became the foundation for the Luger pistol. With the hammer gone, the pistol could become smaller and more compact, though Borchardt's example is far from it!

Not a hammer in sight! The Borchardt is single-action only. It must be manually cocked to fire the first time, then the semiautomatic action takes over.

What does double-action mean?
Double-action means that the trigger cocks the gun AND also releases the hammer/striker. This type of action was perhaps invented in the early part of the 19th century, when repeating guns first began to be popular. At first it was called a "self-cocking" lock, meaning that the trigger did all the work, and it was found on pepperbox pistols as early as 1830. When the revolver became popular around 1850, the trigger also had to do one more thing - it had to advance the cylinder so a fresh cartridge would be ready to shoot each time. That's why revolvers always have a heavier trigger pull, but the striker-cocking action is also why double-action only (DAO) semiautomatic pistols also have a heavier pull.

A pepperbox is an early type of revolver that rotated the barrels instead of a cylinder. Just the top barrel fired at one time.

What does this have to do with airguns?
Everything, because airguns are also either single- or double-action. Some can be fired either way. The S&W 586 revolver, for instance, is both single and double-action. Most of the Umarex pistols are double-action only, because they have no way to cock the hammer other than the trigger. The Walther PPK/S BB pistol, however, is single-action only. You can pull the trigger with the slide forward and the hammer down and nothing will happen. Once it begins firing, however, the slide cocks the hammer for the next shot - not unlike the M1911A1 pistol we looked at earlier.

This is mostly about handguns - but not always
There are a few revolving rifles, too. The Crosman 1077 is one. It's a double-action only revolver with a 12-shot pellet clip. The Crosman Nightstalker is a semiautomatic, but the clip advances by means of the trigger, so it is the world's only DAO semiauto rifle (I think!). That's why it has a heavier trigger-pull than the Drulov DU-10 Eagle semiautomatic rifle.


At April 07, 2006 9:37 AM, Blogger airgundoc said...

I'm a little confused. What would you call the Umarex version of the 1911A?
It seems to be both single and double action but after this blog, I'm not sure.

At April 07, 2006 10:45 AM, Anonymous B.B. Pelletier said...


The Umarex version of the M1911A1 is both single and double action, as you say. The reason most Umarex pistols are double action, even when the firearm they copy isn't, like the Colt, is because they don't have a slide coming back to cock the hammer. If they weren't double action, you would have to thumb the hammer back every time, and no one is going to do that with a 1911.

But consider the Walther PPK/S BB pistol. The firearm it copies is both single and double action, but the Umarex BB gun is ONLY single action. Pulling on the trigger does nothing if the hammer isn't already cocked. But this pistol does have a moving slide to cock the hammer after every shot, so they get away with this design.



At April 07, 2006 1:08 PM, Blogger airgundoc said...

Thanks, that clarifies it quite a bit. That also explains why my Walther CP99 compact has to be manually cocked as the CO2 cylinder pressure gets low. It is by the way a bit irritating to have to do that when the only alternative is to waste some of the gas by changing canisters. That particular bb gun isn't especially accurate in my hands anyway but it is fun to chase cans with it.

At April 08, 2006 10:36 AM, Anonymous Jed said...

This is off topic but I posted about the crosman phantom and B.B. you said it seemed like the gamo shadow for performance but you wont be testing it for a while.I dont know the performance of a gamo shadow but what I do know is I was trying to decide if I should wait for the crosman phantom to come out and learn on its power accuracy and performance,or just buy the ben/sherridan legacy 1000,I have been bassically looking fdor a good magnum airgun for a cheap price,I dont know much aout it but I know benjamin guns are are known for quality.I am just not sure if I should bother to wait to see what the pahantom will be like or not.

At April 08, 2006 3:28 PM, Anonymous B.B. Pelletier said...


I will be testing a Legacy soon. Crosman is sending me one, and they said it would be in April.


At April 08, 2006 11:54 PM, Anonymous POYANCO said...


I dont want to sound the wrong way but,

I was reading the hw97 and hw77 post and I wanted to ask you,coul you make another one?
But this time talk about FP's,specs and important info.Im not saying that the one you did was bad but it lacks info.I mean,if at one time you owned the gun,you could do something like the tx200 post.THAT is a good post.Compare them yourself and please think about it.

Once again,I dont mean to be rude.I just want to tell you what I think.No hard feelings


At April 08, 2006 11:56 PM, Anonymous JDB said...


Have to agree with this poyanco guy.You should make a post worthy of the hw97 and hw77.


At April 09, 2006 1:46 AM, Anonymous Anonymous said...


have you tested the Gladiator and the S-16? I want to buy one or the other scoped with bipod but don,t have the luxury of being able to shoot before buying.

I'm looking for Quality, Power, Quiet report, and a good off hand shooter.

The scope is another thing, I am thinking of Leapers mini 3-12X44 AO. But I am seeing these rifles pictured with 4-15X56 AO full length scope. Scope question is will the mini fit right on the S-16 and do you think the S-16 will need the bigger scope for offhand balance?


At April 09, 2006 8:52 AM, Blogger B.B. Pelletier said...

Gladiator and S-16,

I haven't tested either rifle, but I have held the S-16 at the SHOT Show. It's very heavy for its size! Being made of steel instead of aluminum adds three pounds to the weight.

Both rifles come from FX of Sweden, though I believe the S-16 is actually made in Bosnia. There isn't much I can say about either one, because I haven't tested them. I read about them on the forums but that is the extent of my knowledge.

As far as the Leapers scope are concerned, I have tested all of them. What do you mean about the fit of the mini on the S-16? I don't understand your question.

As far as balance goes, since the S-16 is already so heavy, I think the less weight the scope adds, the better.


At April 09, 2006 9:17 AM, Blogger B.B. Pelletier said...


I'm sorry my HW77 and 97 posting missed the mark. I'll try again this week.


At April 09, 2006 10:37 AM, Anonymous Anonymous said...


Thanks for the feedback on the Gladiatot / S-16. As far as the scopes go, I will probably go with the smaller one. It's one I'm used to in the full version.

At April 09, 2006 11:28 AM, Anonymous Anonymous said...

BB, (or anyone, manufacturers included)

Is there a reason why we can't have a quiet high powered multi shot Tactical style pcp that weighs 5.5lbs?

At April 09, 2006 11:55 AM, Anonymous Anonymous said...


Any info on FX Storm?

At April 09, 2006 4:23 PM, Anonymous POYANCO said...


Thanks and may I suggest some pictures of the rifles.Thanks again and im looking forward to it.

:- ]



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