S&W 686 strain screw replacement

[hkcavalier]

I just had a gunsmith friend of mine look at my 686-4. It's had some light strike issues. After taking it apart, we fixed a bind issue with the mainspring, but he also thought that the strain screw had been shortened. I bought it used about 2 years ago and the previous owner had done some trigger work...amateur gunsmithing (hey I am guilty of that too).

I can't find one online anywhere! I did see a thread on THR re: some gunsmiths using a SS Allen head set screw instead --- makes it adjustable. I also saw some mention of a gunsmith making these specific to S&W revolvers, specifically to fit in the groove on Wolff aftermarket mainsprings (which I have installed in my gun)

Anyone know of this mystery gunsmith and whether or not they are available? If not, what is the thread size on a 686 round butt? I can always go down to a big box hardware store and get it myself and grind to length.

 

[hkcavalier]

Ehh just needed to search the forum a little. I found this thread: http://smith-wessonforum.com/s-w-smithing/159194-strain-screw-vs-wolf-main-spring.html

But not sure if 8-32 is for both N and L frames?

 

[JM4151]

686 Strain Screw Replacenent

I would try calling smith, they might have them in stock. If you need dependability in a gun, they are not something to mess with. Brownell's might also have them. A temp fix might be installing a piece of steel shim stock between the tip of the screw and the main spring. I would start about .008 and work my way up, if needed. The correct way is a new screw.
Brownells # is 800 741 0015. You can get S & W's # from their web site.

 

[OKFC05]

Grade 8, 8-32 capscrews can be ground to any length strain screw you want. Ordinary soft screws peen over and shorten with use.

 

[hkcavalier]

Yeah I checked Brownell's, MidwayUSA, Numrich --- all the usual places plus a Google search ten different ways.

I think I am going to do the 8-32 set screw deal and report back my results. From what I've read, you get it to where they are no light strikes with cheap ammo, mark it, apply Loc-Tite, and then put it back with another half turn extra for good measure.

 

[tomcatt51]

I think I am going to do the 8-32 set screw deal and report back my results. From what I've read, you get it to where they are no light strikes with cheap ammo, mark it, apply Loc-Tite, and then put it back with another half turn extra for good measure.

Use a socket head, be it a socket set screw, button head socket cap screw or socket head cap screw. They're grade 8 and won't have a self shortening deforming tip like the S&W SS strain screws do.

290 Loctite is for assembled fasteners. It wicks in, no disassembly required. Very handy on strain screws. Adjust it, then just add a drop of Loctite.

If you're using a stock mainspring there's a limit to how much less you can preload the spring before you create geometry issues.

 

[SW CQB 45]

If you are a reloader.....just take a spent small pistol primer.....clean out the guts and you have a spacer to fit over your strain screw tip. If that's not enough....take a spent large pistol primer.....clean out the guts and insert the small primer into the large and install on your strain screw tip.

 

[hkcavalier]

So I got a 8-32 3/8" set screw at a local hardware store.

I screwed it in until there was no visible change in the mainspring, then backed it off just a tad. This is a full factory power Wolff mainspring by the way.

There is noticeable deformation on the end of the factory strain screw.

I noticed right away the trigger pull was heavier (I do not have a way to measure this, sadly). The other side effect is the SA trigger pull is now very light. Not quite as light as, say, an old High Standard Supermatic or competition air rifle, but certainly under 1lb. There is now a very small takeup in DA and absolutely zero in SA (as I would expect).

Did I put too much tension on the mainspring? Any other advice would be helpful. In trained hands I don't think it's unsafe. In untrained hands it could be a real surprise.

 

[tomcatt51]

I noticed right away the trigger pull was heavier (I do not have a way to measure this, sadly). The other side effect is the SA trigger pull is now very light. There is now a very small takeup in DA and absolutely zero in SA (as I would expect)

I have no idea what you're saying here.

You'll end up with the DA and SA pull BOTH being heavier (more mainspring preload) than what you had if you want the light strikes to go away which I thought that was the idea.

With a 3/8" long set screw I would expect you need to screw it in so it's close to flush with the bottom of the strain screws' counterbore in the grip frame.

 

[hkcavalier]

It's a little deeper than flush.

The DA pull is heavier. Cocked back in SA, pull is now very light. Getting the hammer back is a little more difficult now, as I'd expect.

Does that make sense?

 

[Seven High]

Are you still looking for a stainless steel strain screw? If so, call the Gun Garage at 479-524-2038. I have bought several from him. They have to be shortened to fit.

 

[derek45auto]

MIDWAY has them

$1.99

Smith & Wesson Strain Screw S&W 625 627 629 686 Round Butt

 

[MR.G]

The head on the Midway screw does appear to be thinner than the original, as stated in the comments. It looks one that I got from S&W. The end is rounded and fits in the Wolf Power Rib mainspring.

 

[stu1ritter]

Anyone have a listing of the length of the strain screws for the different frame sizes. Under-head to end of screw size. It would be nice to be able to accurately grind an 8-32 cap screw to the correct size and not play with it.
thanks,

 

[smithandwessonguy]

I have new S&W screws in stock. PM me if you want one.