I put a reduced power return spring and mainspring in my M66-6. now the trigger stacks. what is causing this?

You will need to post some specifics on the spring set to get a really sound answer. At this point I'll just post what I have learned by making mistakes when tweaking the action in my revolvers.

Mistake One, did you find a pin inside the rebound spring? It's common to the N frames and acts as a trigger stop. However, I have heard that some smiths have also equipped some K frames with this pin durig an action job. If you do have this pin, flip it end for end from where it is right now because it will cause binding on the coils of the rebound spring if it's installed backwards and can tie up the action completely.

I also found out when playing with the tension screw on my 610 that reducing the tension too far will cause the trigger to bind in a double action stroke. Make sure the tension for that new mainspring is all the way tight, otherwise you may find a similar issue with your model 66.

BTW, my preference for springs in an action tuning are a 14 lbs. rebound spring and the factory mainspring tension tightened fully or shimmed out by 1/2 turn at most. While it won't produce the lightest possible DA pull, it does result in reliable trigger reset and reliable ignition with any ammo I've tried. I've also found that reducing the DA trigger pull too much results in a SA trigger that is uncomfortably light. With a DA pull in the 7 to 7.5 lbs range the SA trigger will drop well below 2 lbs. unless some custom work is done to the SA sear surfaces.

Did you use a Wolf Power Rib mainspring?

yes I am using the reduced power rib spring and an extended firing pin from Cilinder and slide

Did you tighten the strain screw fully? Are the angles the same as the original spring?

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NRA Benefactor Member

See if your rebound block is hitting the mainspring when cocked. If so, the strain screw is in the rib of the mainspring and there is not enough tension on it. I have had to use a slightly longer strain screw, or modify the rebound block when using a main spring with a rib to keep the rebound block from hitting the mainspring.

Where would I find a slightly longer screw?

You don't have to, just put a shim between the screw and the spring. I don't however think that's the problem. I think you've put something back together wrong.

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So many S&W's, so few funds!!

Hopefully squiggy got his original problem fixed.

He's re-posting a different question to his 6 & 1/2 year old thread.

.

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We gotta hold onto what we got

Doh! My bad!

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So many S&W's, so few funds!!

The length of the original strain screw may be some too short if it hits into the "groove" on the power rib. You need an extended strain screw.

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H Richard
SWCA1967 SWHF244

When using a Power Rib mainspring where the original strain screw is too short, you can make it go in deeper by chucking the screw in a drill motor or drill press and file some off the bottom of the screw head while it is spinning. This effectively makes the screw you have longer because it will go in further and bend the mainspring more.

The strain screw is 8-32, so a grade 8 capscrew can be ground to suit any length.

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Science plus Art

Or, you can use an 8-32 x 1/2 socket set screw and blue LocTite.

Check with Wolff Springs, they now have longer strain screws available.

Unfortunately, I am still dealing with the same problem. My old place of employment got new ownership, and became very unpleasant to work at. I took a job at a start up brewery in the city. Life changed a lot, and I do not get to play with my guns that much anymore. I still have not fixed this problem. I will look into ordering a screw from WOLFF springs this weekend. Thanks for all the replies.

Wolff had an update to their mainsprings, there were some that were binding with the trigger rebound slide, talk to Wolff about when you got your mainspring.
Do you have aftermarket grips on the gun? Try the trigger with the grips removed, at times the the mainspring will arch and bind on the screw that holds the grips together if you have this style of grips.
Karl