Recontoured Main Spring

[Bob McGee]

What effect does recontouring, or re-curving the main spring have on double action trigger pull? In my own testing it seemed to me that the re-curved main spring, allowed for a lighter pull at the start of the trigger stroke. But what happens to lock time? Also it seems to me when using one of Randy Lee's supper hammers, that I have to run a heavier main spring setting to get reliable ignition, with the re-curved main spring. I hope this hasn't been covered before, as I really would like some information on this facet of trigger tuning.

Bob McGee

[bountyhunter]

I generally do a "mandrel bend" (using a curved tube to bend against) on the upper 1/2 of the spring. I believe the Mikulek aftermarket springs use this method as well. I bend by feel and know what my ammo needs to light off. Bending does reduce the spring force (obviously) that's why you get a lighter DA pull.

Changing hammers may require more spring force (or less) depending on mass and velocity to get the same striking energy.

[Carmoney]

Also it seems to me when using one of Randy Lee's supper hammers, that I have to run a heavier main spring setting to get reliable ignition

No, it should be the exact opposite. A lighter hammer (whether Randy's or homemade) should allow reliable ignition with less mainspring tension than you could ever get away with using a stock hammer. Actually, being able to lighten up the spring is the primary point of the whole lightening effort, although there are other side benefits such as reduced "jiggle" when the hammer falls, and the cool mod-rod look.

[Bob McGee]

Also it seems to me when using one of Randy Lee's supper hammers, that I have to run a heavier main spring setting to get reliable ignition

No, it should be the exact opposite. A lighter hammer (whether Randy's or homemade) should allow reliable ignition with less mainspring tension than you could ever get away with using a stock hammer. Actually, being able to lighten up the spring is the primary point of the whole lightening effort, although there are other side benefits such as reduced "jiggle" when the hammer falls, and the cool mod-rod look.

Carmoney,

The point that I was tring to make was that I thought that with the re-curved main spring it took more spring pressure than with the std. S&W flat spring. I am able to get the double action pull down to 4lbs with the "Randy Lee hammer". However, with the re-curved main spring it seems that I have to go to about 4 1/2lbs to get the same reliability. I am just searching for the ultimate combination, and was hoping for a discution of the merits of the re-curved main spring, as compared to the std. spring.

Maybe Randy could comment.

Bob Mcgee

[Randy Lee]

The effect of the altered mainspring on ignition really depends upon how and where the recurve is located, as well as to what degree the bend.

Also, factory springs act differently from lot to lot and even spring to spring.

When I bend a spring, it is to affect the transition of the the DA sear to the trigger cam surface and to the final DA ledge on the trigger. The goal is a linear force transition. Too much bend at the top can have an adverse effect on the feel of the pull, as well as ignition.

I have seen samples of bent mainsprings which actually decelerated the hammer prior to the hammer contacting the firing pin.

Care must also be taken to ensure the prongs of the mainspring are perpendicular to the stirrup and not canted. This will cause the hammer to list to one side and cause drag which will affect ignition.

A proper bend should only smooth out the first part of the trigger stroke and not affect ignition.

[Bob McGee]

The effect of the altered mainspring on ignition really depends upon how and where the recurve is located, as well as to what degree the bend.

Also, factory springs act differently from lot to lot and even spring to spring.

When I bend a spring, it is to affect the transition of the the DA sear to the trigger cam surface and to the final DA ledge on the trigger. The goal is a linear force transition. Too much bend at the top can have an adverse effect on the feel of the pull, as well as ignition.

I have seen samples of bent mainsprings which actually decelerated the hammer prior to the hammer contacting the firing pin.

Care must also be taken to ensure the prongs of the mainspring are perpendicular to the stirrup and not canted. This will cause the hammer to list to one side and cause drag which will affect ignition.

A proper bend should only smooth out the first part of the trigger stroke and not affect ignition.

Randy the problem that I see with the re-curved springs that I have done is that the hammer seems to rebound off of the firing pin before I let off on the trigger. I'm not sure but the hammer might not even fully depress the firing pin. If I under stand your reply this could be the result of to much curve at the top of the spring. What I was trying to accomplish was to lighten and smooth a trigger pull at the very beginning of the stroke.

[cooper_999]

I´m very interested in "how-to" bend or recurve a factory spring - at the moment, I´m using a grinded factory spring, but maybe a bending is better? Is it possible for anybody, to post a picture of the spring after bending?

Thanks in advance,

best,

Sascha

btw - just got a Lyman Trigger gauge today - my two 586 are at 6lbs and my 627-8 with the Randy-hammer is at 4lbs 14oz

[Randy Lee]

Bob,

If the hammer is bouncing off the firing pin, check to see if the hammer foot is contacting the rebound slide seat as the hammer falls. I doubt this is the problem, but it's always good to check- I found that overtravel stops which are too long can cause this to occur.

If the curve on the mainspring is too much, the back side may contact the back of the frame before the hammer hits the firing pin. There shouldn't be any contact between the frame and mainspring. I have also seen some grips like Pachmayrs interfere with mainspring function.

~Randy

Edited May 17, 2006 by Randy Lee