New 640 pro cylinder is difficult to open

[Kenneth07ex]

Picked up a NIB 640 Pro today. Seemed to open okay the couple times I opened it during initial inspection. Get it home and the cylinder lock up suddenly binds when trying to open it up. Release button is good, the cylinder just sticks pretty bad.

I checked the ejector rod, but it wasn't loose. Any ideas on what else it might be? Everything seems to be working, albeit a bit rough, but about what I'd expect from a new revolver.

 

[armorer951]

Check closely to see that the center pin is coming fully forward, just past (by a few thousandths) the end of the extractor rod when the thumbpiece is pushed fully forward. Could be a minor adjustment needed there.

If the center pin is a bit short, the end of the extractor rod can catch on the end of the front locking lug when attempting to open the cylinder.

 

[Mike in Reedley]

Check below the extractor star for debris.

 

[Kenneth07ex]

Check closely to see that the center pin is coming fully forward, just past (by a few thousandths) the end of the extractor rod when the thumbpiece is pushed fully forward. Could be a minor adjustment needed there.

If the center pin is a bit short, the end of the extractor rod can catch on the end of the front locking lug when attempting to open the cylinder.

Yes, it's a bit shy of coming up flush with the end. I've dealt with this on a couple of other revolvers. But tbh, those don't come up completely flush with the end of the ejector rod either. They might lightly stick, but are nowhere near the bind I'm getting here. What really seems strange, is that it got so much worse after a short few openings. Making me think that it's something obvious that I'm missing.

 

[Kenneth07ex]

Check below the extractor star for debris.

Good call, since it's never been fired except 2 from the factory, I glanced at it on inspection. Obviously it's clean as a whistle, but I'll give it a closer look.

 

[Kenneth07ex]

I've tried to post a picture of where the extractor star is dragging on the guard. Unfortunately the site says invalid file, I have no idea.

On to the subject at hand. It seems that enough in, and out has now shown where the problem is. It seems that the extractor star is dragging on the way out. I'm talking about the whole star timing teeth, right across including some slight chipping of the hole the hand comes through. There's significant scratching, so I'm pretty sure that's the problem. Question is, what to do? I've cleaned beneath the star, but no noticeable difference. But the star isn't sitting proud of the cylinder or anything, it looks to be recessed a couple of thousandths. Slightly buggered frame screws too, grrr. Shouldn't have ever broke out the magnifier.

 

[armorer951]

See how it feels opening and closing after removing the yoke screw.

 

[Kenneth07ex]

See how it feels opening and closing after removing the yoke screw.

After trying it with the screw out, it's still about the same.

 

[armorer951]

You might try flushing out the cylinder assembly and yoke with some spray like Gun Scrubber or non-chlorinated brake cleaner. Remember to protect your eyes.

There may be some crud or chips floating around in the assembly causing problems.

Just another thing to try.....along with a good cleaning.

 

[JDinAZ]

Picked up a NIB 640 Pro today. Seemed to open okay the couple times I opened it during initial inspection. Get it home and the cylinder lock up suddenly binds when trying to open it up. Release button is good, the cylinder just sticks pretty bad.

I checked the ejector rod, but it wasn't loose. Any ideas on what else it might be? Everything seems to be working, albeit a bit rough, but about what I'd expect from a new revolver.

Your bolt may not be going completely forward

This would make the center pin not fully release from the bushing in the recoil shield.

And would make center pin not travel enough forward to fully disengage locking bolt under barrel

With cylinder open. Does the bolt flush out with the bushing in the recoils shield. Most all the new ones don’t completely flush like the old hand built hand fit guns of yesteryear. But it should be very close You may or may not have to push on the thumb piece a bit

The test is drag your fingernail across it. It should not catch on the bushing.

If it’s not very very close to being flush pop the side plate and see what is keeping the bolt from going completely forward

 

[Bob L]

I had a similar case and discovered that cylinder release screw had loosened slightly and wasn't able to push the pin all the way forward.

 

[Kenneth07ex]

Good suggestions here, but I've tried everything listed. I didn't do a full clean, since it was mostly clean already, but I fully disassembled the crane cylinder assembly. Oiled everything, and wiped it down. It did improve quite a bit, it could use a bit more though. But still, its now just a simple binding, that might be typical of a new set of rough fitting parts. I'd certainly expect better from a new $800 dollar revolver. But it's useable for now, so maybe with use, it'll smooth out fast, and I won't have to do anything else but keep an eye on it as I shoot a few rounds.

Otherwise I really like this revolver. Trigger pull is hard as would be expected. Probably a good 12 pounds. But it's very smooth, and the sights are easy to see, unlike my model 60.

Thanks for all the suggestions guys, I appreciate it, and if anything comes to mind about this issue, please don't hesitate to share, because as I've said, it isn't fixed, but only better.

 

[armorer951]

If the binding persists I would suggest checking to confirm that the yoke is lined up properly with the center pin cavity in the breechface. A lot of binding can occur if the yoke is only slightly out of alignment.

The other thing would be confirming the rear gauge or the "headspace" is correct and in spec. S&W often leaves almost no gauge between the cylinder and the end of the yoke barrel, which results in little or no "wink" or end shake in the cylinder assembly when the cylinder is closed.

The cylinder actually needs some gauge, .001" - .002", commonly called end shake, to operate properly, open and close , and to accommodate dirt and lubricants. If it is very tight here, it may open up some with use.

The cylinder to breechface gap should measure .060" - .068"

 

[Protocall_Design]

The ratchets are supposed to be about .005 below the center boss around the center pin. If the ratchets are dragging on the recoil shield, that is not good.

 

[steelslaver]

How does it cylinder turn with stop held down with something like a thin feeler gauge. 0.000 endshake would cause the center of ratchet to be tight against recoil shield and cylinder to turn a bit stiff.
Dab of oil on barrel lug. A stick under lug tooth can make it difficult to open especially if center pin isn't coming flush.

 

[Kenneth07ex]

How does it cylinder turn with stop held down with something like a thin feeler gauge. 0.000 endshake would cause the center of ratchet to be tight against recoil shield and cylinder to turn a bit stiff.
Dab of oil on barrel lug. A stick under lug tooth can make it difficult to open especially if center pin isn't coming flush.

The cylinder turns about the same regardless of the stop. TBH, it really feels about the same as my model 60-3, which is also a bit harder than
it should be. But it still lightly drags on the shield. It has gotten a bit easier, as its chamfered the trailing edge of the hand slot.

There's no clearance at the shield either. My smallest feeler guage is .0015, and it wouldn't go in from the back side. The front side has a taper, so it obviously slides in there. There's zero end shake when closed. I believe it really needs to go back for a proper professional adjustment.

But on the positive side, the trigger is incredible. Light enough for easy single action, and it's easily staged, with a handy audible, and tactile click before the hammer drops. POA/POI is nearly as good as my 6" 686 from 10 yds, which means that it's more accurate than I can shoot. Not quite as much fun to shoot, but it's heavy enough to still be comfortable shooting .38 special, and +P. It'll likely never see a 357. Nice little pocket gun.

ETA, I finally sorted out my picture issue. Notice the chamfered edge, grrr

 

[stansdds]

Yeah, I see that and that's some poor quality work.

 

[Kenneth07ex]

Yeah, I see that and that's some poor quality work.

You should see some of the imperfections in the finish lol. Craftsmanship and quality control ain't what it used to be. But it sure shoots nice.

 

[michpatriot]

I'd say it'll loosen up after a few hundred full house rounds..

 

[Kenneth07ex]

Got this thing back and the problem seems to be cured. I've only shot it around 50 rounds or maybe less. But it opens great, with no problem.

But in cleaning it, I noticed something not seen before on the other revolvers I've owned. There seems to be a small tab of metal in each of the grooves. Something from the original cutting no doubt. They're on all the grooves, where it looks like the cutter just smeared it across. No better than I shoot, it doesn't seem to make a difference. But I've never seen anything like this before. With my lack of photo skills and equipment, this picture is about as good as it gets, and only shows one, and a part of another. But they're all uniformly the same. What do you guys think? Will it hurt the value?