There is a used 686 that has had the cylinder machined to accept moon clips thereby voiding the warranty.

Measuring the cylinder gap with feeler gauges I obtain a reading of 0.014" which I believe is more than twice the recommended gap.
There is virtually zero endshake so I can only assume that the face of the forcing cone was screwed with (although it doesn't appear to have been modified.

Is this revolver safe to shoot with such a large cylinder gap?
Doses it have to be barreled?

Thanks

That's a lead shaver. Shoot it by yourself with no bystanders

Smith and Wesson will not warranty older pistols.  There is a cutoff year, so that probably isn't an issue at all.

Why not just use moon clips?

I don't understand why there is a gap in the front, unless the cylinder is loose.

If you are concerned, just look for another one.  They are out there.

Why would the bullet be shaved? The timing is perfect...

Without a gap between the cylinder face and the forcing cone the cylinder will not rotate

What is an acceptable gap? .003 to .006 is a commonly quoted figure now and again. Is .014 acceptable? I'd say yes. Revolver forums I searched claimed .001 was likely too tight and would cause issues with power build up jamming the rotation.

That's my question for the experts.

Is a gap of .014 safe being more that twice the recommended gap?

It's possible that it developed some endshake and someone installed cylinder bearings which would move the cylinder back from the barrel/increase the gap.

Edit: If you're curious (and comfortable doing so), you could disassemble the cylinder assembly and check.  If cylinder bearings were installed, you may be able to go with a bit less setback which would slightly increase the endshake but some (about .002 - .004) is typical.

Also, did you check the headspace?

Op, this video may help you. I know you don't have any endshake, but this may close the gap to .008-.006 and get it off your mind.

That's not how it works.  For a rimmed cartridge, like the .38 Special, .357 Magnum, .41 Magnum, etc., when the cylinder is cut for a moon clip a "floor" is milled in the cylinder and in the ejector star to make room for the moon clip.  However, the outer portion of the cylinder is left uncut so that the cartridge can still head space on the rim if the shooter elects not to use a moon clip.  In other words, the rim is still fully supported around about 1/3rd of cartridge's circumference.

There will be a little room between the ejector star and the rim (equal to the thickness of the moon clip, plus some minimal clearance), but the ejector star still has the same effect of ejecting the cartridge cases and the shooter will never notice the difference.

For a rimless round, like the 9mm Luger, .45 ACP, etc, a moon clip must be used for ejection purposes as there is no rim for an ejector star to grab.  However, if you were to fire those rounds in a revolver chambered for that round, it would still head space on the mouth of the case and there'd be no issue with the hammer firmly hitting the primer.

The exception is when you take a .45 Colt or .45 S&W Schofield revolver and have it cut for moon clips for .45 ACP.  In this case, the chamber mouth is a long ways in front of the .45 ACP case mouth, so the only support it has for head spacing is the moon clip itself.

The shims only increase the distance between the barrel and cylinder though correct? In the video his endshake should have been .004” after, if he measured.  The cylinder would still be .010” at full aft position, but I may be wrong.

I do believe you're right. Using that reamer and more bearings would be the only way I could see you getting the cylinder closer to the cone.

Im no expert either, my gunsmithing expertise goes about as far as field stripping a gun to clean it. Haha.

Anyway, there are options I guess.

Call S&W and ask how much to fix it ? They might do it for free. Worth a try .

After a discussion with the dealer who sold it to me, they agreed to pay for any charges incurred to have S&W fix the problem and then sent it off to S&W for repair.
It took almost three weeks from the time it was sent back to when the dealer took delivery of it. Smith & Wesson paid for shipping both ways, replaced the barrel and repaired the crane at no charge.

Frickin' awesome...

I believe Smith says anything up to .012 is in spec.  Yours is just outside of that.   Hard to say how yours got that large; may very well have come from the factory that way.

Edit... just noticed that S&W fixed the issue... congrats and enjoy!

So what does the gap measure now ?

0.006"

Excellent.

Glad to hear about it. Some people bitch about their CS but I have sent them a ton of revolvers in all sorts of states over the years and they have always worked with me to get them up and running. Sometimes I have to pay but a lot of time not. I've been very happy with them most times.

From my email exchange with S&W CS, I fully expected them to require payment for the repair.
Outstanding outcome.

Awesome outcome! I recently sent a newly acquired Smith (used) and they replaced a sticky ejection rod for free. The revolver is like new now. A+ rating from me.