Home Forums Hunting & Shooting Gunsmithing Light primer strike on a S&W 686

Quite a few years ago I had great smith do a trigger job my 686 . It finished out with a crisp and about a 4 pound DA trigger. Now after more than 30,000 rounds when shooting DA, I get light primer strikes that do not fire the round.Maybe 1 in every 12 rounds. The same round fires in SA mode.

Would a new hammer spring fix the problem without increasing trigger pull?

My first thought would be the spring. You could get a Wolff kit and try a couple and see what will cure it and give a similar trigger pull. Any change in primers lately? Some are harder than others.

Is your strain screw screwed in fully?

Yes, check the strain screw and see if it's backed out some. 9 times in 10 that the culprit. If not you'll need a new spring.

I will check that first. No change in any components for years

It's either the strain screw or the mainspring. If you can't just tighten the strain screw, then you need to lengthen it or use a longer one, or change the mainspring for one with greater weight.
To lengthen the strain screw, you can cut under the head to lengthen the shaft. It is preferable to start with a new, full-length screw. Since the smith probably shortened the original screw, you can simply not shorten the new one or shorten it less. You can find the correct length by screwing the new, full-length screw all the way down and then backing it out until you start to get light strikes. Then screw it back in some and measure to cut.

A new spring of the same original weight could be enough to replace a worn spring, but the strain screw length allows a finer tuning than swapping in a heavier mainspring. Personally, the combination that I find works well is a Wolff Power-rib mainspring Type I (full power) mainspring with a full-length S&W factory screw. Be careful to get a full-length screw because S&W has started shipping new screws pre-shortened. The full-length screw works ideally with the Power-rib spring because it goes into the indented center rib of the spring which effectively reduces the spring preload compared to using the same length screw with a flat mainspring. Any shorter screw with the Power-rib Type 1 and some primers won't ignite. The Power-rib Type 2 (reduced power) is pretty much a Federal-primers only deal.

The strain screw is tight. Brownells carries the original factory Main Spring for $5.99 and the std weight Wolf spring for $16.72 or the std weight spring kit for $19.99. Is the Wolf spring all that much better than the factory one? They show the factory Strain Screw for $3.29,but give no length.

I assume I don't need the kit,just the main spring

Thanks in advance.

Vince

I like the Wolff full power spring because they have given me less stacking in the DA trigger pull.

While checking the strain screw for tightness you should also check that the tip that bears on the mainspring has not been shortened. Only way to do that is to compare to a new unaltered strain screw. Some 'smiths shorten the tip of the strain screw to get a reduced trigger pull. Purchase a new strain screw and install, see if that makes the light primer strikes go away.

Thanks Gunwizard. What with the shipping cost of Brownells or Midway, I think I will order the Wolf Spring kit and a new Strain screw.The spring kit is only about $3 more than the main spring by itself

I have used the Wolf spring kit on many of my S & W's, good product never had any problems. Should solve your problem.

Thanks

I have had good experiences with Wolf springs. On the other hand, the stock spring lasted 30,000 rounds. I don’t know if a Wolf spring will last longer than that.

That 30,000 is about where mine is. At my age, I doubt I will do another 30,000. I believe the spring in mine is a replacement done by the pistol smith that worked on my 686 when I first got it.I was doing some action pistol matches then and needed it tuned up

Realizing that this is a gunsmith forum and I am not a gunsmith, I have another small problem and maybe some one has an answer to it.

I bought the Wolf spring kit and a new strain screw form Brownells.The strain screw is listed as the mfgr's one. When I put the Wolf main spring in, the new strain screw was about .090 shorter than the one in the gun. It would not even take up the slack in the Wolf spring or the old spring that was in the gun. Using the old longer strain screw, I installed it in the gun with the new Wolf main spring. It was a tad short as I still got light primer strikes. Since the range is 40 miles away, I put new primers in some fired brass and tested with only the primers( no powder or bullets)

Starting with .020 brass shim stock, I placed it between the end of the old strain screw and the Wolf main spring.This worked, and I had no light primer strikes. I then went to .015 shim stock and repeated.That worked.Then I tried .010 shim stock and again I got light primer strikes. I did not have any .012 shim stock and I did not try .010 and add .002 shim stock to it. I will be going to the range this coming week to test it in live fire and tweak the strain screw.

I don't know if the pistol smith made this old strain screw or if there is supplier that one can be purchased from and modified to the correct length.Anyone know of one?

I could use an 8-32 stainless steel set screw if I could find one long enough or modify an 8-32 fillister head stainless steel screw. Or leave it like it is with the .015 shim stock in it. Or buy another factory main spring and use the factory strain screw

I’ve TIG welded strain screws that were cut short. SS are especially easy since there’s no finish to worry about.

No idea if you have the capability to do this. Just putting it out there as an option or maybe an explanation of what the original gunsmith may have done.

Nope,can't do that.All I have is a 110V wire feed with no cover gas and an old Miller stick welder and I am not all that good with either.

Update. Talked to Tech support at Wolff Springs. They have the correct length strain screw to match the Wolff Main Spring with the ridge in it.