DST mechanics

[BrentD]

On some (most, all?) Double Set Triggers (DST), there are two springs. One resets the main trigger when the set trigger is pulled. The other one works the set trigger and throws the set trigger bar into the sear bar to trip the tumble and set everything in action.

Both of those springs add tension to the set trigger in the set mode. So, while I can adjust the set trigger - to some extent, I am only changing the amount of engagement. When the set trigger adjustment is changed, it really produces more or less creep rather than a heavier or lighter pull.

I believe that if one of the two springs was replaced with a stiffer spring I would get a heavier trigger, which is what I want. I have two target rifles that are really super light when set and sooner or later I'll end up putting a round down range when I don't want to.

So, how does one increase trigger pull properly? With a heavier front trigger spring or the set trigger spring?

Thanks,
Brent

[greybeard]

If trigger is so light that it is dangerous back off the adjustmebite screw between the  two triggers. This will give you a deeper engagement on the bite but will not make the front trigger lighter;  Just give you more front trigger travel.   Bob

[J. Talbert]

The amount of tension on the rear (main) spring of the DST will also affect the trigger pull.
I'm usually trying to lighten it. So I like to tighten the adjustment screw on the main spring only enough to trip the sear.  This usually allows for a lighter pull that is also less prone to let go by accident.

Jeff

[Ted Kramer]

Brent,

If, when using the triggers unset,  the trigger pull is too light, then you may have to increase the tension of the sear spring in the lock. I may be wrong here but I wouldn't think you'd want to increase the tension of the front trigger return spring because then you'd have a heavy trigger pull even when you have the triggers in the "set" position.

Another thing to check is to make sure the sear is free drop all the way into the notches on the tumbler and is not hanging up on some wood in the lock mortise. This could be giving you a hair trigger effect even when the triggers are unset.

Ted

[heinz]

Brent, how light is the pull on your front trigger when the set is not engaged? That pull weight is what is imposed buy the "feather spring" If that is too light you can adjust the feather spring with various methods or make a new one.  If the feather spring feels right and the pull gets lighter when set, you have some angle issues on your trigger engagement.

[bgf]

Heinz brings up a good point -- the geometry affects the pull weight as much as the springs.  I can't see any harm in making the engagement angle more severe to increase the pull weight, if that is possible, but you would want to harden the surface at least.  Perhaps the contact surfaces have worn and altered the original geometry some.  That is just a suspicion, without seeing the actual trigger, its hard to know what would work best.  I know it seems strange to want to make a pull heavier, but I've seen one at least that my fingers were too numb to feel, and it would have been dangerous for me to use.

[Don Getz]

My first question would be.......why did you put a set trigger in the gun if you don't want a "hair" trigger?   Nontheless, you have what you have.   If you want a "harder" pull, I would tighten down on the screw of the rear mainspring, and
loosen the adjusting screw so that you have more engagement of the set trigger.   This will require more effort to release
the trigger.  Other than that, I wouldn't know what to do............that's basically how those triggers work...........Don

[BrentD]

Don, I believe you have missed my point. I have many DST rifles.  Most of them are spot on, but these two are not.  Actually, I could throw in a Ballard DST as well but they are quite a different beast. 

Don, have you ever shot a Bob Roller trigger?  That would be perfect for these rifles, but refitting a Roller trigger into these rifles is not an option.

Angles may be an issue.  @!*% hard for me to determine, but I'm going to have to do better to be sure.  Meanwhile, some experimentation with shimming the front trigger spring suggests that a heavier spring there may get me closer to where I want to be. 

Brent

[Dphariss]

On some (most, all?) Double Set Triggers (DST), there are two springs. One resets the main trigger when the set trigger is pulled. The other one works the set trigger and throws the set trigger bar into the sear bar to trip the tumble and set everything in action.

Both of those springs add tension to the set trigger in the set mode. So, while I can adjust the set trigger - to some extent, I am only changing the amount of engagement. When the set trigger adjustment is changed, it really produces more or less creep rather than a heavier or lighter pull.

I believe that if one of the two springs was replaced with a stiffer spring I would get a heavier trigger, which is what I want. I have two target rifles that are really super light when set and sooner or later I'll end up putting a round down range when I don't want to.

So, how does one increase trigger pull properly? With a heavier front trigger spring or the set trigger spring?

Thanks,
Brent

Here is an explanation of set triggers
http://americanlongrifles.org/forum/index.php?topic=11196.0

There are angles that need to be understood that are not explained by the drawing.

A good set trigger is a light one. Its what they are supposed to be.
If the geometry is wrong the trigger will be much heavier than it should be or dangerously light with the trigger held set by the front trigger spring.
Buy stretching the rear trigger its possible, as explained in the text, to make a very heavy trigger.

Dan

[BrentD]

Thanks for the drawing Dan.  I know what set triggers are supposed to be like and these are just not correct. 

Last night with a bit more experimenting, I was able to improve one of them by shimming the front trigger return spring.  That spring was very very thin and light.  A heavier spring will fix this permanently. 

The other DST has a heavier front spring than the first set, and I suspect it has more problems with angles than anything.  All the adjustment screw does for that trigger is increase the creep.  Doesn't change let-off at all.  I hate to mess with angles over such small spaces, but that may be required.

[keweenaw]

The first thing you want to check on the trigger that is always too light is the wear on the engagement surfaces.  If they aren't absolutely crisp with no indication of rounding, the problem is more likely wear than anything else.   If it shows wear then it's too soft so redressing the surfaces will only delay the problem reappearing.

Tom

[Don Getz]

Brent......you got that right, I have no idea of what your problem is....................Don

[BrentD]

Brent......you got that right, I have no idea of what your problem is....................Don

Thanks for being so helpful   

[Pete G.]

I don't like the idea of increasing the mainspring tension to much more than that required to trip the lock. You are dealing with very small engagement surfaces here and increasing the pressure is usually not a good thing. Most commercial parts are usually a little bit oversized, so you might want to look at reducing the rear edge of the trigger notch in order to require the front or set trigger to travel further forward. This will slightly increase the angle where the engagement surfaces meet. That, along with a tweak on the trigger spring itself usually will give a crisp letoff, but everything has to be in balance with everything else, and everything affects everything else. Save the engagement screw adjustment for last. Adjust one thing at a time, and do so in very small increments and you will get what you are looking for.

[Blacksmoke]

BrentD:    Along with most factory made locks - most DST have to be "tuned" as well. I have done this with lots of them so  I understand your problem completely and recommend that a stronger spring be fashioned for the front triggers of the two rifles that you are having trouble with.    It may be possible to re -adjust and thereby salvage the springs that are in place.  However unless you are you are well experienced  with springs in general I do not recommend doing the adjustment yourself.     I will be happy to examine your triggers and do what ever adjustment is needed to give the proper trigger pull that you desire.  Just remove the triggers and send them to me.              NO CHARGE   - you will only pay the shipping both ways.      Hugh Toenjes

[BrentD]

Hugh, that is a heck of a generous offer and I greatly appreciate it, but I want to learn how to do this, because there will be a day when I just plain have to.  Besides, I like teaching myself new tricks, even if they are simple little ones. 

With that in mind, I experimented with shimming last night and got one of them exactly where I want it.  I used a small metal spacer to raise the front spring slightly but I added a small upward rise to the shim that extended towards the trigger.  It did a nice job of increasing the trigger pull just enough.  I don't think it is too hard on the spring because i made the rise gentle and rolled over on the edge, but I will worry about it a bit so now I'm in the hunt for some stronger spring material. 

The shim may not be the best permanent solution, but it shows me where i\I need to go. That rifle now has a no-creep break that is very light but not whisper light.  The other rifle?  Probably needs a stronger spring but the angles worry me. More experimentation tonight. 

Brent

[Blacksmoke]

Brent:   I appreciate your " I want to do it myself" attitude and I wish you success.    If you get stuck please do not hesitate to contact me - I've been working with this stuff for over 35yrs. and I am here to help.      Hugh Toenjes

[BrentD]

Thanks guy.  That is a great offer.