Lightening Revolver Trigger Pull

3

3006loader

New member
I recently took apart my revolver for a thorough cleaning and when I put it back together I noticed that the double action (and probably single action) trigger pull was noticeably heavier. I believe this is because prior to taking it apart, the hammer spring tension screw was not screwed in all the way, but when I put it back together I screwed it in fully.

So my question is, Is backing out the hammer spring tension screw an effective way to lighten the trigger pull? I am well aware that reliability could be affected negatively, but I am more wondering if it will damage the revolver in any way? The model is a Smith and Wesson 19-3.
 
Not a bad question at all.

When I was a kid I did that very thing (loosened the hammer spring tension screw) and was told by my uncle to never ever, ever do that again. He gave me the technical reason for not doing it. "CAUSE IT SCREWS UP THE GUN!!!" and we left it at that.

Real revolver experts will be along shortly to give you real advice, but let me say again it is NOT a bad question.
 
S&W will tell you that the screw you are referring to is the "strain screw" and that is NOT an adjustment and that it should be screwed in all the way.
 
order you a spring kit from Wolff and change it out. You can file your existing spring to lighten it but if you don't know what your doing it will break over time
 
I think that the OP just wants to know the reasoning behind the NO.

Unreliability is the only reason I can think of, but otherwise, how could the mainspring being under less strain damage the gun?
 
It won't damage the gun, but unless it's fully tightened, it can back out (in fact, a little blue loctite even when it's fully tightened is good insurance). So, even if it's still reliable when set "just so", the gun can become quickly and unpredictability unreliable. For a range gun, it's a nuisance, but a much more serious issue for a SD gun.
 
Another good reason is that if it falls out completely and gets lost, it can be difficult (or nearly impossible) to replace (e.g. square butt k-frame).
 
Machinery, including guns, are designed as a whole.
It's not always obvious to understand how all the parts work together.
Messing with one particular part can cause unintended consequences.
Hence the warning not to mess with anything without knowing how it affects everything else.
 
Well, the screw would get lost, but the main spring is captured inside the grip panels, so unlikely that would get lost.

It was not an uncommon practice in the bullseyes target world to loosen the strain screw to lighten the trigger. Many target grips were notched out for that strain screw, knowing this.
Of course reliability was not as great an issue as it only cost points.
 
Machinery, including guns, are designed as a whole.
It's not always obvious to understand how all the parts work together.
Messing with one particular part can cause unintended consequences.
Hence the warning not to mess with anything without knowing how it affects everything else.
Click to expand...
Can you give an example?
 
I've always thought loosening the strain screw wasn't a good option because there's no way to really keep it from backing out more and more until its too loose. Having the screw tightened keeps a constant tension.

I've heard a better option is to shorten the strain screw or buy a replacement and modify it so you can resort back to the original if wanted. Filing or sanding down the screw gets the same result but let's you fully tighten the screw.

Swapping out the mainspring or trigger return spring are also options to bring down the trigger pull weight.
 
reddog81 said:
I've heard a better option is to shorten the strain screw or buy a replacement and modify it so you can resort back to the original if wanted. Filing or sanding down the screw gets the same result but let's you fully tighten the screw.

Swapping out the mainspring or trigger return spring are also options to bring down the trigger pull weight.
Click to expand...

Shortening the strain screw isn't a much better option, IMO. For one thing, as mentioned, it can be difficult to replace. For another, the strengths of the main and return springs are designed to be balanced, since they work in concert.

I should note that simply swapping springs (even if they're balanced) does nothing for the quality (smoothness, consistency, letoff, etc) of the trigger. If these need work, the gun needs a good action job, which is much more than swapping springs (or dry firing the beejeebers out of it).

I should also note that changing the mainspring tension alone (either by messing with the strain screw or by putting in a lighter main) does little or nothing for the single action trigger weight - the mainspring tensions the hammer, but it's only the trigger (not the hammer) that gets pulled back when pulling the SA trigger. If you want to lighten the SA trigger, you need to lighten the return spring, which is what tensions the trigger.
 
I should also note that changing the mainspring tension alone (either by messing with the strain screw or by putting in a lighter main) does little or nothing for the single action trigger weight - the mainspring tensions the hammer, but it's only the trigger (not the hammer) that gets pulled back when pulling the SA trigger. If you want to lighten the SA trigger, you need to lighten the return spring, which is what tensions the trigger.
Click to expand...
Of all the S&W double actions I have owned and shot, none of them had anything other than a superb single-action trigger pull. As such, I do not understand why it would need improving. On the other hand, the double-action pulls of stock S&W's have been needlessly heavy and benefit from action work and lighter springs. The only reason I can think of for improving the single action pull is just, "because we can." But even then, screwing with the single action notch and the related part of the hammer, because the engagement is so small, is risky as hell.
 
...the strengths of the main and return springs are designed to be balanced, since they work in concert.
Click to expand...
Can you explain exactly how they are designed to work in concert and what would happen if they did not?
 
Of all the S&W double actions I have owned and shot, none of them had anything other than a superb single-action trigger pull. As such, I do not understand why it would need improving. On the other hand, the double-action pulls of stock S&W's have been needlessly heavy and benefit from action work and lighter springs. The only reason I can think of for improving the single action pull is just, "because we can." But even then, screwing with the single action notch and the related part of the hammer, because the engagement is so small, is risky as hell.
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^ This!
 
Howdy

Shooters have been backing out the strain screw on Smith and Wesson revolvers to lighten the trigger pull for over 100 years. GENERALLY SPEAKING, it will not damage anything.

HOWEVER..................if you back the screw out too far, it will cause a problem. Back the screw out enough and you will notice the hammer suddenly becomes much more difficult to cock.

When the strain screw is torqued all the way in, it affects the shape of the spring. Back it out a bit, and the bent shape of the spring changes slightly. Back it out too much and there is a problem.

This is a view of the hammer fully cocked with the strain screw torqued all the way in. The piece the spring is hooked under is called the stirrup. The stirrup is pinned to the hammer, and swings through a slot in the hammer to engage the mainspring in all aspects of rotation.

hammer%20spring%20compression%20normal_zps7nycgigb.jpg





In this photo I have backed the strain screw out too far. I am encountering resistance to the hammer going back all the way to full cock. What is happening is the new curve the spring took is forcing the stirrup to pivot too far. You can see the change in the angle. The stirrup has swung as far as the slot in the hammer will allow, and now it is binding against the body of the hammer.

hammer%20spring%20compression%20strain%20screw%20backed%20out%202%20turns_zps4e6vag72.jpg




It just so happens the revolver I used for these photos is a Model 19-3 made in 1975. But this will happen with any S&W revolver made with traditional forged and machined parts. What really surprised me was it only took backing the strain screw out two full turns to get the hammer to bind up like this. If I backed it out much more, it would probably damage something, most likely damaging the stirrup by putting too much pressure on it. I did not try backing the screw out any more to see.

Backing the strain screw out enough to bind up the stirrup this way will vary from revolver to revolver, mostly depending on how deep the slot is in the hammer. But I was quite surprised that it only took two full turns on this Model 19 to get the hammer to bind up.

I have not tried this with a S&W revolver made with MIM parts. I do know that the MIM hammer and trigger have been substantially redesigned from the earlier forged and machined parts. I do not know if this phenomenon of binding up the stirrup on a MIM hammer will happen or not.

An experiment for another day.



With any revolver, either single action or double action, when the hammer is cocked in single action mode, the hammer spring forces the cocking notch of the hammer hard against the sear with a certain amount of force. When the trigger is pulled, the force against the sear causes friction as the sear slides out of the notch. This friction is in addition to the force required to overcome the rebound slide spring. By lightening the hammer spring, you are reducing that amount of friction so it requires less force on the trigger to slide the sear out of the notch. That is why backing out the strain screw on a S&W revolver affects the single action trigger pull.

The old trick with a Colt Single Action Army was to place a leather spacer between the hammer spring and the frame, effectively reducing the force the hammer spring exerted on the hammer. I have reduced the trigger pull in Colts to 2 1/2 pounds by simply grinding down the hammer spring, without doing anything else.

In double action mode there are two springs that affect trigger pull in a S&W revolver. The hammer spring or main spring, and the rebound slide spring. Competition shooters have known for many years that they can lighten the double action trigger pull by grinding the rebound slide spring shorter. You can try clipping it, but the spring is pretty tough. Competition shooters also know that by lightening the rebound slide spring, the trigger will not return as crisply after every double action shot. So there is a balance that must be struck.

You can try filing the hammer spring, but you will be there all day and you will accomplish nothing. The spring steel of the hammer spring is much too tough and a file will not touch it. To lighten the hammer spring you have to grind it. And yes, it is very easy to screw up and ruin the spring.

I absolutely recommend against messing with the engagement of the single action sear in a S&W revolver and the trigger. Do not even think about it unless you know exactly what you are doing. You could make the gun unsafe very easily.

If you want to buy springs from Wolff, you can buy a kit that includes a reduced power hammer spring, and three reduced power rebound slide springs, so you can fine tune the trigger pull.

Of course replacing the rebound spring in a S&W revolver is the trickiest part of putting the gun back together again, but if the OP successfully reassembled his Model 19, he should be able to replace the rebound slide spring without launching it across the basement to hide in the most inaccessible spot in the room. Don't ask me how I know about this.

There is a tool you can buy from Brownells that makes changing the rebound slide spring a little bit easier.
 
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Driftwood Johnson said:
By lightening the hammer spring, you are reducing that amount of friction so it requires less force on the trigger to slide the sear out of the notch. That is why backing out the strain screw on a S&W revolver affects the single action trigger pull.
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That amount of friction is small compared to spring tension. If you progressively back out the strain screw and measure the DA and SA trigger pull weights with good gauge, you'll see that the SA weight barely changes. I actually did the experiment myself, but the curious one ought to give it a try.
 
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