I’ve got a 686-6 (the SSR Pro model) that exhibits vertical stringing with every load I’ve tried in it. These loads have proven quite accurate (1-2” @ 20 yards) in my 64,65 and 66 – and my 686-5, but for some reason they will only give me 4-5” groups @ 15 yards in the 686-6. The groups vary only by about 1” horizontally, but balloon up to 5” vertically. The gun locks up nice and tight and the b/c gap is a consistent .004” on all six chambers. What I do notice is the finish on the crown is a little rough and I actually get leading in the recess (it’s a recessed crown). Could a rough crown give you vertical stringing? The gun is as slick as snot, but the accuracy level is gonna keep me from using the gun for IDPA unless I can get it resolved.

I think you have hit on it. Take it to a trusted gunsmith and have re-crowned. I think you will notice a distinct difference.

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H Richard
SWCA1967 SWHF244

Curious as to the logic behind this recommendation. Why would re-crowning be responsible for vertical stringing? The most common causes are the barrel heating up - especially rifles - and shooter breath control.
Remember that b/c gap is not a measure of how accurate your revolver will be. Alignment of the cylinder with the barrel and a square forcing cone are what is needed. I would offer the following possibilities instead of crowning problems. 1). b/c gap is too small for this model. 2). Forcing cone not correctly and smoothly cut 3). Forcing cone not square with the frame. 4). Cylinder face not square to the frame 5). Barrel got squashed too severely with S&W mounting technique - measure with bore micrometer. 6). Cylinders not in alignment with f/c.
Sparks

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Its not that simple.

Call the factory and explain the problem. It should be a warranty issue. If you do some field mods, warranty will not correct them if they don't work.

Are you doing your part in shooting the gun?
Let others shoot it and see if they get the same
results. Also if you are useing cast bullets are they
the right diameter for your barrel. Just somthing
to think about. Don

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"Don't worry be happy"

Stringing is ussually a load thing....

Crown will just throw fliers wherever....(mossberg the target as we say)

The most common load problem which causes vertical stringing is inconsistent (high) primer seating, at least in my experience.

B.

The owner states that the same ammo works great in other guns. So I have to assume the problem lies elsewhere. Agree with shovel that a bad crown will result in fliers. Find a feeler gauge that will just fit between f/c and cylinder face. Use some felt marker on the rear face of the f/c. Close the cylinder and gently insert the gauge from both right and left sides. Inspect f/c for uneven removal of marker, which would indicate an unsquare condition. Do this test after firing 20 rounds to be certain that you still have a f/c gap.

Second test requires a brass cylinder about 3" long mounted to a metal rod. The brass cylinder is machined so it just fits into the end of the barrel. As it is moved down the barrel, 2 things can be checked. If the brass cylinder becomes tight or obstructed at the barrel threads, you have a squashed barrel at the threads. Pushing further, you can check each cylinder's alignment with the bore. These 2 checks will probably turn up the cause of your problem. I am suggesting these tests because in my experience the gun will be returned to you as NPF.

Sparks

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Its not that simple.

Find a gunsmith that will recrown,extend and deepen the throat on your barrel by one caliber in your case .357.

Ken

I would send it to Smith & Wesson without wasting any time at all

I would first check the strain screw. Some people will sometimes back the screw out when they are trying to sell the revolver. This will lighten the action making it seem like a trigger job. Sounds like inconsistent primer ignition. A spring kit can do the same thing. Also check the primer hits.

Backing out the strain screw any more than 1/4 turn will effect ignition IME. I have fixed some trigger jobs by removing the anvil from a spent primer and inserting it over the strain screw. That was all it took to get it working. I dont recommend this as a permanent fix.

Just a thought;what sort of grips are on the gun? If they are "rubber" try some wooden ones and make sure there is no looseness between them and the grip frame.

BEFORE doing anything to the gun, I'd let another good experienced and accurate shooter try it and see how it performs. If there is no stringing then you know it is not the gun.

Anyone realize this thread is an antique?

That said the biggest cause of vertical stringing I see is from guys resting the gun butt (bottom of the grips) on something while shooting groups.