Trigger happy: Part 2

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1

In Part 1, we looked at single-stage and two-stage triggers. Today, the focus is on single-action and double-action triggers. Is that confusing? Does a single-action trigger sound like a single-stage trigger to you? If it does, you are in the majority, because this confuses a lot of folks — some of them are even writers in the shooting sports! Edith told me about an airgun company that doesn’t appear to know the difference…thinking that double-action and two-stage and single-action and single-stage are the same things but just stated differently.

History
It may help if I go back to the very first trigger and explain how it worked. In the very early days of shooting, there were no triggers at all. A lit piece of cord called a match was carried by the shooter; and when he wanted to fire his gun, the (hopefully) hot coal on the end of the match was touched to a hole located at the rear of the barrel. That’s where the term touchhole comes from. The hot match would hopefully ignite some of the gunpowder that was at the top of the touchhole and hopefully the tiny explosion would go all the way down the touchhole and hopefully ignite the main powder charge.

How many times did I write “hopefully” in the last paragraph? Four, which is my way of saying that these early hand-cannons were not that reliable. If you make one today, it’ll seem very reliable, but that’s just a comment on how good today’s black powder has become. The early powder was far weaker and harder to ignite, the matches often went out — especially in the rain — and the length, size and shape of the touchhole had a profound influence on the success or failure of the gun’s ignition.

In time it all got sorted out. The powder got better and shooters learned how to care for their matches. At some point in time, a clever mechanic attached the match to an iron rod that was attached to a pivot on the hand-cannon and shaped so the lit match end fell exactly on the touchhole. The other end of the rod was shaped to be easy to operate with the fingers of the hand that held the gun. Thus the first trigger was born. This first trigger did not have a sear. It was just a lever. If you bumped it when the gun was loaded and caused the match to hit the touchhole — oh, oh! But at least they didn’t shoot themselves while cleaning their guns — at least not accidentally!

By the middle 1500s (and probably earlier), we had triggers with sears. They were needed when the wheellock mechanism came along. A wheellock is a cigarette lighter built into a gun. It has a powerful spring that’s tensioned by winding with a lever or key. The spring causes a large, serrated steel wheel to turn; and when a piece of pyrite is held against it, sparks are generated.

The tension of the mainspring has to be restrained so the shooter can select when he wants the gun to fire. A sear is a type of dog or restraining lever that blocks the wheel that’s under tension. The trigger then becomes another lever that trips the sear (releases the dog) so the wheel can turn, generating sparks and igniting the powder charge. This kind of trigger was a single-action trigger. That means you first had to cock the gun (by winding the spring) before the trigger was put in place by another small spring to hold the sear.

With a single-action trigger the gun must first be cocked by some outside activity before the trigger can be set to perform its job. I don’t have a wheellock to show you but I do have a French 1822 flintlock military pistol that’s been converted to percussion. The trigger on this pistol works the same way I’ve described. The hammer must first be cocked or the trigger can do nothing. When the hammer is cocked, internal springs have pushed the trigger to block the sear from moving. At this point, the trigger can release the sear when it’s pulled, allowing the hammer to fall. It’s very similar to the wheellock, except that if the gun is a flintlock, the lock generates the spark for ignition through the striking of flint, rather than the dragging of pyrite against a steel wheel. In a percussion gun such as my 1822 French pistol (a flintlock-to-percussion conversion), the hammer falls on a percussion cap that explodes, igniting the black powder.

1822 French martial pistton and Colt single action
The trigger of the 1822 French martial pistol (top) just flops around loose until the hammer is pulled back to the cocked position. Then, the trigger is held in place to block the sear (on the hammer) by a small spring. When you pull the trigger until it moves out of the sear notch on the hammer, the hammer falls and explodes the percussion cap. The cowboy gun below is called a single-action revolver and works in a similar fashion, interestingly enough.

And that was how all triggers were until the mid-19th century. Don’t let set triggers confuse you. They existed well before this time, and they’re all single-action.

Double-action triggers
The double-action trigger was probably first produced in England or Belgium around the middle of the 19th century. My vote goes to England. Some clever mechanic found a way to link the trigger blade to both the sear and a second lever that pushed the hammer back against its spring. Now, the trigger could do two things. It could release the sear and could also cock the gun. And it could do both of them at the same time, with the result that the gun fired every time the trigger was pulled. Cocking the hammer first went from being a necessity to an option.

Ruger Security Six
You can almost always spot a double-action revolver by the trigger positioned far forward in the trigger guard.

The advantages of the double-action trigger are many. First, it allows you to fire the gun with no other action. Just pull the trigger and eventually the gun fires. On most guns, it gives you the option of also cocking the hammer separately and firing the gun single-action. The single-action trigger-pull is much lighter than the double-action pull. All it does is release the sear. But the double-action pull also has to compress the hammer spring, and that makes a double-action trigger-pull heavier.

The effect of the trigger on shooting
Because it’s lighter and crisper, a single-action trigger-pull results in more control over the handgun. Therefore, it’s always used for formal target shooting. A double-action pull usually results in pulling the shot to the side opposite the hand that holds the gun. In other words, a right-handed shooter will pull his shots to the left when shooting double-action. It’s possible to train yourself to shoot accurately this way, however, and since double-action is faster than single-action, it’s used when revolvers have to be shot quickly.

With a semiautomatic pistol, you can have both. The gun can function as a double-action for the first trigger pull; but once the slide pushes the hammer back to the cocked position, it’s now a single-action until the gun is empty. Or, you can just cock the hammer manually for the first shot and it’s single-action all the way.

And, because double-action triggers require more effort, they’re viewed as safer in the hands of those with less handgun training. So, some semiautomatic pistols have a double-action-only trigger-pull. The Glock is most famous for this.

What to take away from this
The thing to remember is that a single-action trigger-pull means just causing the sear to let go and fire the gun. The gun has to be cocked separately and by something other than the trigger. A double-action pull means also putting tension on the hammer spring, so the gun fires with each pull of the trigger without anything else needing to happen.

29 Responses to “Trigger happy: Part 2”

  • Anonymous Says:

    B.B.,
    Came across this one on straightening barrels at the FX factory.
    http://www.youtube.com/watch?v=V_HTQ…eature=related.

    Found it interesting. What do you think of the new smooth twist barrels?

    Pete

    • chuckj Says:

      Pete,
      I couldn’t get your link to work.
      -Chuckj

      • Pete in the Caribbean Says:

        Chuck,
        Dono what happened with the link. try Googling Smooth twist barrels at the Fx Factory being made and tested.
        Looks like Air Arms is now testing the smooth twist barrels in some of their rifles. My guess is that it is cheaper to rifle the barrels this way.
        Hope you can locate it-the owner of FX was showing off an FX Independence in 25 cal which was tuned to put out 70 ft lb.

        pete

    • B.B. Pelletier Says:

      Pete,

      All I know about smooth twist barrels is what I have read. They seem to be very picky about ammo, but also very accurate under the right conditions.

      B.B.

  • Chris Legate Says:

    Thank you Mr. Gaylord.

    This report has solved some things for me. I especially appreciated the “wheel-lock” explanation. I have had this explained to be before, but it was WAY to technical (I am a mechanical engineer by trade if that tells you anything about the previous explanations.) and I found this very easy to understand.

    Can’t wait to read you post everyday!

    Thank you!

    • B.B. Pelletier Says:

      Chris,

      Thanks for your feedback. I think I need to write reports like this from time to time, because these fundamental things are not well understood, in many cases.

      B.B.

      • Desertdweller Says:

        B.B.

        Thanks for the explanation of this. This is a topic that I think causes confusion even among gun enthusiasts. It is good to get a straightforward explanation, and the links BG provided help to further illustrate it.

        Les

      • J-F Says:

        True! It’s here that I learned the difference between single and double action, one or two stage triggers in what seems like such a long time now.

        J-F

  • BG_Farmer Says:

    BB,
    I would have taken some pictures of flintlocks/parts if you wanted. The ones below are online, but the vendor doesn’t compete with PA, so I hope it will be OK.

    Here’s a link to the backside of a flintlock:
    http://www.trackofthewolf.com/Categories/PartDetail.aspx/749/1/LOCK-KL-FL-RH

    The sear is the thing at the back — the sear bar extends horizontally over the trigger. Basically, the sear is a pawl that holds the tumbler (a notched wheel to which the hammer is attached) in position, and it (the sear) has a “crank handle”. You can see the sear and tumbler here:
    http://www.trackofthewolf.com/Categories/PartDetail.aspx/773/1/LOCK-SL-LH-UP

    The trigger is either a simple lever that trips the sear when pulled or a set trigger that whacks it with spring loaded lever. There is not usually a spring in a simple trigger, but the sear bar may contact the trigger when the lock is cocked and thus hold it steady (due to the sear spring in the lock). Here is a simple trigger:
    http://www.trackofthewolf.com/Categories/PartDetail.aspx/920/2/TR-FG-1-T
    The simple trigger is usually pinned in the wood of the stock, although it can be pinned into a trigger plate as well, but you lose leverage when the pivot point is too low.

    Most of the sidelock designs (flintlock or percussion) work this way, though there are some variants among the mule-ears, for example.

    • BG_Farmer Says:

      Go to “view 2″ to see the backside of the lock; I thought it was linked directly, but I was wrong.

    • B.B. Pelletier Says:

      BG_Farmer,

      Thanks. It wasn’t a flintlock I wanted. It was a wheellock. Pyramyd Air has a strict policy of not grabbing pictures from other websites without permission, so I didn’t.

      My pistol is a converted flintlock, so the backside of the lock looks the same.

      B.B.

  • Jim in KS Says:

    B.B. -

    Like Chris, I look forward to reading your blog post each morning. Over the years, I have learned an awful lot about the airguns and techniques that you write about. Technique is something that I’ve been meaning to talk to you about. You are well-known for promoting the artillery hold, which you have described on numerous occasions, yet, from time to time, you talk about varying your technique to shoot off the backs of your fingers, change the location of the hand on the stock, etc.

    By experimenting on my own, I have found that I can predictably change the point of impact by shifting my left hand forward or back. Even more interestingly, I have found that I can change the size of the groups by changing the shape of the hand that the gun is resting on.

    Here’s an example: By resting the rifle on its balance point, across a relaxed open palm, with no finger contact on either side, the results are pretty good… ten yard five shot groups of about .375 inch, with varying irregular shapes. By curling my fingers toward me so the rifle rests only on the firm pad at the base of my index finger, groups shrink to less than .25 inch and get very round in shape. A few five shot groups will still hold a pellet in the hole.

    I’m not stating that any of my results are definitive. But they certainly are curious, aren’t they? What would you think of organizing your own experiences with various spring guns, and writing a series on resting hand technique?

    - Jim in KS

    • B.B. Pelletier Says:

      Jim,

      Thanks for your encouraging words. Like you, I have noticed these small holding changes bring big differences on target — sometimes. Some guns are twitchy while others seem pretty stable.

      And there are those occasions where I do shoot best resting directly on the bag.

      B.B.

  • Primo Says:

    Does the trigger pull on the Glock compare in weight to say a SW 38,or does the Glock have an adjustable trigger pull. And if the Glock trigger is adjustable can it be adjusted by a common user or does this have to performed by a gunsmith?

    • B.B. Pelletier Says:

      Primo,

      A Glock trigger pull is “adjusted” by installing different springs. It isn’t hard to do, by any Glock gunsmith will tell you they should do it.

      And no, a Glock DA pull doesn’t come close to a Smith %& Wesson DA pull. The Glock is more like a Colt revolver, in that the pull stacks.

      B.B.

      • Mike Says:

        BB, to change the trigger pull on a Glock you change the “Connector”. It is a flat, angled piece of metal. Most civilian Glocks come from the factory with a 5.5 lb connector installed. Heavier and lighter ones are available. They aren’t hard to change as you noted but you do need to know how to detail strip the pistol. I like the 5 lb connector for everyday use. It is only a 1/2 lb less but you can feel it.

        Mike

  • Matt61 Says:

    Fascinating textbook material here. I didn’t realize that there was a significant delay for the wheelock while the wheel spun under tension to create a spark for ignition. I’m trying to make another effort to understand creep. This corresponds to the movement of the trigger while it is sliding along the sear. Is that right?

    B.B., thanks for the explanation of eye relief and notch sights. But if the goal is to focus on the front sight anyway what difference does it make if the rear notches are sharp or not?

    Victor sounds like you’re shooting again with your old form. That’s great.

    Okay, everyone, exercise your constitutional right and vote and we’ll see where the chips fall. Never in my life have I seen a presidential election like this one. I cannot imagine what either one of these candidates have gone through during the campaign. For such as myself who dislike large crowds and gladhanding, their regime would be worse than a daily bullwhipping. Anyway, come what may, we will continue to promote the joys of airgunning and the shooting sports.

    Matt61

    • B.B. Pelletier Says:

      Matt,

      The reason the rear notch needs to be sharp is that when you sight through it you align the front sight element with the rear notch. As in the tip of the front sight aligns with the top of the rear sight.

      When you look through as peep sight, the peep hole aligns your eye automatically because the light in the center of the hole is the strongest. So the peep sight is automatic, but with the notch sight, you are doing the alignment.

      B.B.

    • Victor Says:

      Matt61,

      Yes, I’m trying to shoot as often as I can. But I need to pace myself. I haven’t tried shooting pistol yet, but I’ve been thinking about it in recent days. The last time I tried (a couple years ago) my hip and left leg went through pain and numbness. Physical therapy has done wonders to alleviate the painful effects of degeneration of 4 disk’s, so it’s coming along slowly. Now I have other issues that I’ll need to overcome, like balance. I don’t want to get into all of that here, but I’ve got some challenges ahead of me. Bottom line is that I need to get all of my shooting in while I still can.

      Between 2 and 3 years ago I was shooting often and proving to myself that a lot of low-cost air-rifles were surprisingly accurate. It took months in some cases to master a particular rifle. With each rifle it was a learning process. Learning to shoot my first springer, after having extensive experience shooting firearms, made me feel like I was starting all over again. But because I had already gone through the ropes of taking myself through the ranks as a competitive marksman, the process of mastering each air-rifle was not too difficult. It was always just a matter of time. As I’ve said before, to be a good shooter you have to be a good problem solver. If you’re too easily discouraged, then you’ll miss the opportunity to experience personal accomplishment.

      Victor

  • Mr B. Says:

    Ladies and Gentleman,

    Today is a very special day in my household. My youngest child voted for the first time! To all of you I say please exercise your God given right to vote.

    Bruce

  • twotalon Says:

    A little slow today so….

    There are three five shot groups and one ten shot group. Distance 9 1/2 yds. If you number the groups from left to right, which one is the ten shot ?
    http://i189.photobucket.com/albums/z244/twotalon/006.jpg

    twotalon

    • Victor Says:

      TwoTalon,

      Nice groups! What gun were you shooting, and what type and weight of pellet did you use?

      Victor

      • twotalon Says:

        A slightly modifried AA T200, H&N FMR 4.51 . Benched. If I tried that offhand, I might not have hit the back wall.

        twotalon

      • twotalon Says:

        Victor…
        No guess at which one is the 10 shot ? Looks can be decieving. (no, I did not purposely blow any of the groups).

        twotalon

        • Victor Says:

          TwoTalon,

          I’m guessing that the 3rd group has 10 shots. The first two groups were so good that they gave you confidence to go from 5 to 10 shots. It looks like you’ve got some ricochets that bounced almost straight back.

          Victor

          • twotalon Says:

            Victor…
            Nope…not the third group. That narrows it down to the first two.
            Just a couple details….
            I was running out of air when I started. It was off the curve by a long way when I finished.
            Also, I did not shoot the groups in order….I shot 1, 3,4,then 2.
            I do get pellets bouncing back out of the duct seal at times. Never know what direction they will go.

            twotalon

    • chuckj Says:

      twotalon,
      You forgot to include that fifth target that has the 10 shot group. The temptation is to point to the fourth one but I have a feeling that’s not it. It’s too obvious. You have some incredible groups there, my friend. I have been resisting that rifle for three years now so quit tempting me. When I first joined this blog there was an individual who was always singing the laurels of that rifle. I never fully understood why because I never saw one shoot. Looks like you have taken up the banner and given me proof.
      -Chuck

      • twotalon Says:

        chuckj…
        The last group would be the obvious choice, but it is not it. That narrows it down. Maybe tried too hard on that one.
        This rifle is not stock. I was very pleased with it at first, except for a terribly crap barrel. A real shotgun.
        Shoots over the chrono like it is on a regulator. I did some things with it besides replacing the barrel. Jacking the the M.V. a bit is included. Don’t know what it is with the match pellets, but is just over 600 with Exact RS.

        twotalon

  • john Says:

    Been working on my ak47 today. Remade a third reciever. I’m getting way better at it but for some reason the bolt carrier will not function properly. The trigger, which is the simplest trigger unit I have ever seen works beautifully though. I’m using the original single hook ak-47 the gun came with in 1963. (yeah, this is a real romanian combat weapon.) For what it’s worth, I set the same reciever up for an AMD65 and tried it. It worked beautifully. Cycled like a new gun. So, no clue why the ak47 isn’t cycling.

    For those of you that don’t know what an AMD65 is, It’s a more compact version of an AK47 developed by the hungarians to be used by anphibious assault forces, vehicle crews, and special combat operators. Same caliber as ak-47 and same rate of fire.

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