S&W 686 light hammer strikes ??

[mikle76]

My 686 has a ftf about every 1 in 6 rounds. It is clearly due to a light primer strike but the odd thing is that all of the fired rounds will have very good dimples with the one misfire being very lightly dimpled. It occurs with random chambers and most times the second attempt at firing works just fine. Any ideas on the problem?

 

[Oro]

Most common causes are:

1) Loose main spring screw. It is easily accessed on the lower 1/3 of the grip strap (down below the trigger guard). If you have target or other type grips, you will need to remove them to access it. It is the slotted screw beneath the ring finger of your strong hand when gripping the gun.

2) Replacement of the original mainspring with a reduced power one, combined with hard primers. Inspect the mainspring to see if it's factory or aftermarket (post a picture, someone can tell you - the aftermarket ones are from Wolff and usually ribbed, factory ones are flat).

Check these items, also if the mainspring screw is tight, remove it and examine the tip of it to see if someone has filed on it to shorten it. There are other possibilities, but these two would cover 95% of the cases. Easy, cheap to fix, don't worry too much yet.

I am guessing the gun is new to you and bought used? New guns should not do this at all.

 

[easyrider604]

all of the fired rounds will have very good dimples

When a round fires, it will recoil back into the recoil shield and firing pin. That's why I think all fired primers have uniform deep dimples.

with the one misfire being very lightly dimpled

As Oro said above, you may have a weak mainspring or the adjustment screw at the bottom on the frontstrap needs to be tightened (turned clockwise).

If that doesn't work, you may have too much headspace caused by excessive cylinder endplay (cylinder front-back movement). In most of my revolvers, I can feel very very little endplay, can't give actual measurements though. Some resident experts here can explain "endplay" better.

If your problem is not endplay, it could be the hammer dragging as it falls. Not likely on Smiths.

 

[MrBorland]

it could be the hammer dragging as it falls. Not likely on Smiths.

Unless your Smith has rubber grips and the grips screw was over tightened, in which case the mainspring can get pinched a bit - enough to cause light hammer strikes. Seems this is pretty rare, but sounds like a possibility and it's easy enough to check and fix.

 

[easyrider604]

grips screw was over tightened, in which case the mainspring can get pinched a bit - enough to cause light hammer strikes

+1 Good point, MrB

Happened to me. Binding mainspring caused by overtightening Pachmayr type rubber grips is quite easy to do and difficult to diagnose if you are not aware of it. Drove me crazy because the grips are not mechanically part of the action, so I wasn't looking there for the problem/solution.

This problem will not occur with Hogues.

 

[cinteal]

almost always the hammer spring screw. Take the grip off, tighten the spring, you should see a difference. Firing double action you should see even more ftfs. Remember, tightening the tension on the mainspring also affects double action pull, so take a flat screwdriver to the range with you and adjust to your liking.

 

[The Lone Haranguer]

Are you the original owner? Someone may have tampered with it, perhaps changing a mainspring, loosening the strain screw (it is supposed to be cinched down against a shoulder, not an adjustment), or even shortening the strain screw.

 

[rcmodel]

Any chance you are shooting reloads?

A primer that is not fully seated can do exactly what you are describing.

First strike finishes seating it in the case with the anvil against the primer compound.
Second strike fires it.

It's uncommon in revolvers because usually a high primer will bind up cylinder rotation.
But not always.

rc

 

[mikle76]

Thanks guys. It happens with reloads and factory ammo. I backed the mainspring screw out and tightened it back down and the problem has gotten less frequent but is still an issue. Time for a new one ya think?? It was a used gun before I bought it and I can see that the screw head is a little buggered up from the previous owner(s).

 

[Deanimator]

shortening the strain screw.

+10,000

I bought an ex-police 3" S&W Model 65 from CDNN. It's a great gun, but I got constant light hits. The first thing my smith checked was the strain screw, and it was tightened down. He didn't figure it was the strain screw because typically it's bullseye shooters who shorten the strain screws on Model 14s and Model 25s. Turns out it had indeed been shortened. He replaced it and it's been 100% since.

 

[18DAI]

What dash number is your 686?

If after checking the strain screw, and following the other suggestions offered, your 686 still gets light strikes, it may be the firing pin is too short.

In order to pass California drop tests, S&W has shortened the firing pins on it's revolvers. This is in the 686-6 and later lock equipped revolvers. Replacing it with a firing pin from Apex Tactical, or Cylinder & Slide will eliminate the problem. Good luck!

 

[Maelstrom]

Pull the cylinder and put six rounds in it. Look across the top. Do all of the rounds appear to be the same depth. Worst case would be a cylinder that was machined improperly.

A lot of calipers have a depth gauge built in. You could check depth from rim to cylinder face.

 

[mikle76]

What is a strain screw? I think it is a -3 to -5 model (but heck if I know for sure..how can I tell?) It is factory pre-drilled but does not have the lock.

 

[Jim K]

The strain screw on a flat spring type S&W is in the lower front of the grip. It provides tension to the flat mainspring. Turning it out a bit reduces spring tension and is sometimes (wrongly) used to reduce trigger pull. Rather than have the screw head sticking out, some people file down the inside end of the screw. Both practices are bad because they can result in misfires.

Jim

Hi, Thaddeus Jones,

That is the first time I have heard about S&W shortening the firing pin to pass a drop test. Can you confirm that or cite something from S&W to that effect?

Jim

 

[The Lone Haranguer]

The grips may have to be removed to see the screw.

 

[mikle76]

Ok, that's the screw I tightened back down already. Maybe time for a new screw and spring. Thanks guys.

 

[18DAI]

Hi Jim Keenan,

I don't have a cite, there have been several threads over on the blue forum concerning this topic. A gunsmith named Grant Cunningham has also spoken to this topic IIRC.

My knowlege of it came about when I purchased a 3" 65-5. It was NIB. The revolver started to misfire on one chamber after about 24 rounds. Then after 36 rounds, on two chambers. It got progressively worse. The strain screw was tight, and the primer showed a very light imprint.

I went to my gunsmith, and he told me about S&W shortening the firing pins. He replaced the pin with one from Cylinder & Slide, and the 65 functioned normally after that. Alas I had lost confidence in it, and sold it.

That was the beginning of my dislike for current production S&W revolvers. None of my extensive collection of S&W revolvers ever has given me a problem.

I had a similar firing pin problem with a 686-5 2.5" as well. I can't confirm it was the firing pin in that case, as I returned it to my dealer and got a refund. TJ

 

[18DAI]

mikle76 you can see what model number your 686 is by opening the cylinder, and looking at the frame inside the yoke. It is stamped there.

I'm guessing that you have a 686-5. Your local gunsmith should be able to swap the firing pin out for you for minimal cost.

Just for curiosity sake, open your cylinder, and after checking to see the revolver is empty, spin the cylinder. Does the end of the ejector rod wobble? If it does, its bent and may contribute to your problems. TJ

 

[solvability]

You can get an oversize firing pin and sometimes that will help - depends on model. (internal firing pin)

 

[Hawk]

Here's one from Stainz I saved which would come in handy if your 686 is an earlier square butt with the newly hard to come by strain screw.

http://www.thehighroad.org/showpost.php?p=5247528&postcount=9

Handy if someone has taken a file to a strain screw.

 

[mikle76]

I'm going to take my Hogues back off and take a second look at the possibility of a shortened screw. I wish there was a gunsmith around here worth using. There is nothing quite like driving an hour, waiting for 3 months then have a GS tell you all the gun needed (Rem. 7400) was cleaning, charging me $60 to clean it and still have the same easily identified malfunction. ARRGGH!! Faith in the GS goes right out the window....

 

[Deanimator]

I'm going to take my Hogues back off and take a second look at the possibility of a shortened screw.

Strain screws are cheap and should be widely available from Gun Parts Corp and Brownell's.

 

[Hawk]

Strain screws are cheap and should be widely available from Gun Parts Corp and Brownell's.

Not if you're talking square butt.

http://www.e-gunparts.com/product.asp?chrProductSKU=301560
http://www.brownells.com/aspx/NS/st...p=15170&title=STRAIN SCREW, SQUARE BUTT, BLUE

S&W dropping the square butt has caught up to the parts guys, it would seem.

 

[Old Fuff]

I suspect that if people keep bugging the two above mentioned suppliers, one or both will have some screws run by an independent maker. Both have built their businesses by offering what the manufacturers have discontinued. Some years back S&W changed to standard screw threads to replace the oddball ones they had made for generations.

The Old Fuff will investigate further...