New S&W N-Frame Mainspring NOT Compatible with Vintage Models?

[Ethan Verity]

I bought a brand new factory S&W mainspring for my Model 29-2, only to realize it doesn't work! The new spring looks near identical to the original spring, apart from it being a little more flat when not installed. I put the new spring in, and the trigger pull weight was off the charts heavy! That's when I noticed, the new Model 29-10 (current production) holds the mainspring under less of a bend than the old model 29-2. Reference my attached pictures, looking at where the spring notch is on the bottom grip of the two models. I don't have the strain screws in for those pictures, but the Model 29-2 holds the spring base closer to the front of the gun resulting in more of a bend than the 29-10 does. Specifically, reference the spring bottom in relation to the grip centering pin, that pin is in the same relative location on both guns.

Model 29-2 made in 1977


Model 29-10 made in 2019


As a result, a new production mainspring does not have the correct shape from the factory for an old Model 29-2, and gives it an extremely high trigger pull weight if installed in the older model.

Has anyone else experienced this problem when restoring an older model N-Frame? Does the new spring simply need to be bent into more of a C shape, or are the spring properties completely different all together? In all the posts I've seen talking about the older guns, I have never seen it mentioned that new production mainsprings are not compatible with older guns. At least not without some modifications I suppose. Having to manually bend the new spring into shape is going to take a lot of force, and a lot of test fitting to get the pull weight where it should be.

Definitely something to be aware of, if you have an older N-frame in need of a new mainspring.

 

[Jonesy814]

You could always back the strain scene out to get the appropriate trigger pull then loctite it in place

 

[StrawHat]

You could always back the strain scene out to get the appropriate trigger pull then loctite it in place

That would work but I would prefer to buy a new strain screw, perhaps a set screw, and file it to fit. Then snug it up tight and have no protrusion out the front of the grip strap.


Here is a photo of a Model 25-2 I received where the strain screw had been backed out. Can you imagine trying to shoot it like that?



A previous owner had rounded the grip frame and relaxed the strain screw to do an “action job”. There was a pair of wrap-a-rounds installed so this was not noticed. The shop I got it from stated it had a terrible trigger pull and it did. Snugging up the strain screw helped but it was still too long for using magnas.

Kevin

 

[Col. Harrumph]

Maybe Wolff has the old spring?

 

[PapaG]

The last two spring kits I bought for K, L frame Smiths had a mainspring too short to use.

 

[Dave T]

I'm not surprised a new production mainspring doesn't work properly in older revolvers. Smith has stated publicly they do not support older models and no longer have parts for them.

And by the way, I like that 25-2. It has great potential. What did they cut that barrel down to?

Dave

 

[Master Blaster]

These springs work great in my old and new Smith & Wesson revolvers.

https://www.gunsprings.com/SMITH & WESSON/K, L, & N FRAME/cID3/mID58/dID264

 

[Ethan Verity]

These springs work great in my old and new Smith & Wesson revolvers.

https://www.gunsprings.com/SMITH & WESSON/K, L, & N FRAME/cID3/mID58/dID264

Good to know! Do you get the factory standard, or reduced power? Also, did you measure the pull weight? I would like to maintain the factory trigger pull weight. I don't want to mess around with potential ignition problems, since I sometimes carry my 29 in bear country.

 

[Ethan Verity]

I'm not surprised a new production mainspring doesn't work properly in older revolvers. Smith has stated publicly they do not support older models and no longer have parts for them.

And by the way, I like that 25-2. It has great potential. What did they cut that barrel down to?

Dave

Some parts work, some don't.... the mainspring surprised me though, since they looked near identical.

 

[StrawHat]

I'm not surprised a new production mainspring doesn't work properly in older revolvers. Smith has stated publicly they do not support older models and no longer have parts for them.

And by the way, I like that 25-2. It has great potential. What did they cut that barrel down to?

Dave

Dave,

Yes, it does have some appeal, which is why I bought it. That and it came with this.



This is a 4” barrel with a Patridge foresight. The other was cut to 3 1/4” or maybe 3 1/2”, let’s compromise and call it 3 3/8”. But, it was shortened with a chopsaw and crowned with a cobble! The muzzle was off square by at least 8 degrees and no front sight. We are packing the house for a move so the revolver and barrel are at Andy Horvath where he will install the 4” barrel and fit a McGivern bead to the Patridge. It will weigh a bit more than my Mountain Gun and Foothills Revolver (both 45 ACP), but it will ride in the same holster.

Kevin

 

[Paul7]

I'm not surprised a new production mainspring doesn't work properly in older revolvers. Smith has stated publicly they do not support older models and no longer have parts for them.

Dave

It isn't just Colt.

 

[sigwally]

I learned something today, thanks.