Model 10-8 Sticky Spot in Cylinder Rotation

[stanmerrell]

I have an old model 10 that I have been using to help learn about gunsmithing on the K frame. I rebarreled it awhile back and it works good except for a spot in the cylinder rotation that is a little sticky. It works fine, but seems to be binding somewhere. I added an end shake bearing which seemed to make the problem worse, so I was thinking that maybe I should trim a little off the crane? It seems to maybe be dragging in one spot on the recoil shield...Appreciate your suggestions.

 

[Alk8944]

Have you thoroughly cleaned the gun, including thoroughly brushing the back side of the extractor and its recess in the cylinder?

If this happened after the re-barrel the barrel-cylinder gap may be too narrow. The factory would fix this by hand filing the breech end of the barrel in place! If the cylinder is dragging on the barrel it should be obvious from drag/wear marks on the barrel breech and cylinder face. If the matter got worse by adding an end-shake bearing this is a different issue. Simply remove the added bearing! This should be obvious.

One reason why you may see the sticking in one place is because S&W cylinders are rarely perfectly square resulting in a high spot on the cylinder face that can cause binding on the barrel if the b-c gap is too small.

 

[stanmerrell]

Feedback

Have you thoroughly cleaned the gun, including thoroughly brushing the back side of the extractor and its recess in the cylinder?

If this happened after the re-barrel the barrel-cylinder gap may be too narrow. The factory would fix this by hand filing the breech end of the barrel in place! If the cylinder is dragging on the barrel it should be obvious from drag/wear marks on the barrel breech and cylinder face. If the matter got worse by adding an end-shake bearing this is a different issue. Simply remove the added bearing! This should be obvious.

One reason why you may see the sticking in one place is because S&W cylinders are rarely perfectly square resulting in a high spot on the cylinder face that can cause binding on the barrel if the b-c gap is too small.

The gun is super clean everywhere. I know this can cause bind8ng if there's anything under the star, but it's clean. The bc gap is good. I removed the bearing but the issue still exists just not as much. Thank you.

 

[Shotguncoach]

You mentioned that it seemed to be binding on the recoil shield. A Model 10 should have enough clearance that the cylinder never gets closer than .060" to the recoil shield.....perhaps does the issue only happen when there are cases in the chambers?

The answer to that question will lead to other questions. Does it behave the same way when it is empty, when the chambers have empty cases in them, and when it is actively being shot at the range? Does it lock up or does the trigger pull just get harder? If the trigger pull gets harder, is it at the beginning, middle, or end of the stroke? If you cycle the action with only one empty case in one chamber, does it always bind in the same place regardless of which chamber has the empty case in it, does the binding occur randomly, or is there one chamber that binds and the others are fine? Does it only happen when the trigger is cycled double action or does the binding happen in single action as well? Have you measured the rim thickness of the ammo to ensure that it is within specs?

Most importantly, what other work was done to it besides the rebarrel?

 

[Shotguncoach]

The reason behind all the questions above is that I spent quite a bit of time chasing a similar problem with a Model 66 that had been previously worked on. In my case the gun worked beautifully when it was empty, but at the range it would randomly have problems ranging from increased double action trigger pull to completely locking up. I chased cylinder rotation issues for a while and then finally realized that whoever had worked on it previously had messed up the double action sear and the trigger bevel. I replaced the hammer and trigger with a set from a Model 10 as a test and that fixed the problem. The stainless and case-hardened mix looks nice to me so I left it that way instead of trying to correct the damage to the original parts.

In other words, if you can't find the problem with the cylinder rotation look at what else is moving at the same time......

 

[stanmerrell]

Thanks

You mentioned that it seemed to be binding on the recoil shield. A Model 10 should have enough clearance that the cylinder never gets closer than .060" to the recoil shield.....perhaps does the issue only happen when there are cases in the chambers?

The answer to that question will lead to other questions. Does it behave the same way when it is empty, when the chambers have empty cases in them, and when it is actively being shot at the range? Does it lock up or does the trigger pull just get harder? If the trigger pull gets harder, is it at the beginning, middle, or end of the stroke? If you cycle the action with only one empty case in one chamber, does it always bind in the same place regardless of which chamber has the empty case in it, does the binding occur randomly, or is there one chamber that binds and the others are fine? Does it only happen when the trigger is cycled double action or does the binding happen in single action as well? Have you measured the rim thickness of the ammo to ensure that it is within specs?

Most importantly, what other work was done to it besides the rebarrel?

Thanks. The gun behaves the same loaded or empty. The trigger pull is just a little harder, but enough so that you know something is not right. Happens in both SA and DA. Seems like it's hardest on one spot in the rotation that is about mid way through the da trigger pull. No other work was performed, but I had to change the extractor, since it went from 2" to 4" barrel. Seems like something is making the cylinder push against the recoil shield, which makes me think the crane might need a very slight trim. I might try some other parts as you suggested I have a lot of them here.

 

[Vtgw938]

OP: Mark the end of the yoke tube with marker and rotate the cylinder a bunch of times to see if the bearing surface is all the way around. If there is still some marker spots on the end than it is likely out of square. The contact points will be bare metal where the marker wore off. Where there is still marker is a "low" spot. I use a Lee case trimmer to square up the yoke tube.

 

[stanmerrell]

OP: Mark the end of the yoke tube with marker and rotate the cylinder a bunch of times to see if the bearing surface is all the way around. If there is still some marker spots on the end than it is likely out of square. The contact points will be bare metal where the marker wore off. Where there is still marker is a "low" spot. I use a Lee case trimmer to square up the yoke tube.

Thanks. I'm gonna try that and will report back.

 

[stanmerrell]

There does seem to be a high spot that quickly wore off my marker. I'm gonna order that case trimmer and see if it helps square things up. Thanks.

 

[Vtgw938]

There does seem to be a high spot that quickly wore off my marker. I'm gonna order that case trimmer and see if it helps square things up. Thanks.

Mark the bearing surface of the yoke before you cut so you can see your progress and go easy. Even though the trimmer is for brass it easily cuts the yoke steel. Check for burrs inside and out and you can lightly polish up the end with a stone or fine sandpaper.

 

[Vtgw938]

OP:

I am now chasing a similar problem of my own. I thought I had the problem resolved but it apparently persists. Cylinder binds up a bit on a couple chambers. It is not the end of the yoke in my case. I thought I had isolated it when I took the locking bolt out of the barrel shroud but it persists when the extractor rod is free.

 

[armorer951]

If the revolver does this when cycled with the cylinder open, then you can rule out the problems associated with the cylinder assembly and yoke as being the cause. (front locking bolt, yoke misalignment, extractor rod runout, etc.)
This would also rule out problems with the bearing surface at the end of the yoke barrel. BTW, removing material from the end of the yoke barrel can have catastrophic results. If the specifications regarding the rear gage or "headspace", and the front gage or "B/C gap" are correct, then endshake is a moot point.

The likely cause if the resistance is felt when the gun is cycled (DA) with the cylinder removed would be wear or damage to the double action sear.

Early onset of this wear produces a "bump" or resistance in the trigger pull about half-way back to release. This resistance is caused by the fact that the DA camming surfaces on the trigger and hammer come into contact with each other as the transfer of force occurs during the hand off from the sear to these camming surfaces. Leading edges of these two camming surfaces should not touch until the "hand off" from the sear has been completed.

A new sear can be installed and fit to the gun, which, if installed and fit properly, will remedy the problem.


Carter

 

[Vtgw938]

In my case it does not do it with the cylinder open. I'm not sure the surface that the end of the yoke contacts in the cylinder is square.

 

[stanmerrell]

Update, I trimmed the yoke barrel a little bit. It was out of square, and is correct now, but did not change the condition. I only took about 0.005" off, with no perceptible change in performance. I'm not sure how you cycle the gun without the cylinder in, but I think I figured it out once and will try that too. I spent a little time on straightening the extractor rod and tried a replacement extractor rod, and it seems to have solved some of the issue. There's still a hard spot on one or two of the cylinders. I may look at the internals next, since I've been wanting to learn about them. Comments appreciated.

 

[armorer951]

Open the cylinder, hold the thumbpiece back, cycle the action.

(Warning: never cycle the action under spring tension with the sideplate off)

Can you check your barrel/cylinder gap? It's now .005" smaller, and your headspace is .005" larger.
There would be no reason to trim the end of the yoke barrel unless you're fitting a new yoke or cylinder.



If you're interested in learning about Smith and Wesson revolvers, you should consider purchasing Jerry Kuhnhausen's book, The S&W Revolvers, A Shop Manual, 5th Edition.



Carter

 

[HeloMt]

As Carter mentioned in the post above, cycle the revolver with the cylinder open (or removed completely). In either case, hold the thumbpiece to the rear to cycle the action double action. If the binding is still present, it is a sear issue. If not, a cylinder rotational issue. Since you've checked the ejector rod, I'd look at at yoke alignment next.

 

[Vtgw938]

Yoke alignment is right on. It is one of the few proper tools I have. It might be the mating surface to the yoke face down in the cylinder.

 

[Alk8944]

Update, I trimmed the yoke barrel a little bit. It was out of square, and is correct now, but did not change the condition. I only took about 0.005" off, with no perceptible change in performance. There's still a hard spot on one or two of the cylinders. I may look at the internals next, since I've been wanting to learn about them. Comments appreciated.

Several things. Does the cylinder have any end shake at all? If you took .005" off the yoke arbor it should have some. It needs to have about .001-2" at minimum, but very little more. If you can feel any end shake there should be enough clearance between the ratchet and breech face. If not then the yoke could still be the problem.

If you pull the hammer back to lower the cylinder stop so that the cylinder can be freely rotated by hand while latched into the frame does the cylinder turn freely then, or is the bind just when the cylinder is closed and noticed when cocking either single or double action?

Maybe I asked this in my first post in this thread, but did you have the binding problem before re-barrelling the gun? If not then you need to be looking at things related to that change. It is not impossible that the frame is distorted (bent, warped, "tweaked", pick the word! It is not impossible the gas ring is binding on the yoke too. I did see this once on a revolver that had just been returned from repairs at the factory!

Then there is a matter of nomenclature. Revolvers have one cylinder, the cylinder contains several chambers aka charge holes!

If you haven't cured the problem with what have already done you really need to have someone look at the gun who understands the S&W mechanism better than you. No insult intended, just fact. I say this because there is one thing that is paramount, don't cut or file anything until you are sure you know where the problem is, Unfortunately you have already violated this.

Just trying to give you all the possibilities.

 

[stanmerrell]

Thanks all. Problem seems rotational rather than the internals, since when I operate the action with the cylinder open, condition is not present. I'm going to look at the yoke alignment next, as some of you have suggested. I think I changed the yoke/cylinder when I re-bareled it, so a likely cause. I still have a pretty tight BC gap, and the breech/ratchet space seems about right. With the hammer slightly pulled back, the cylinder rotates freely until the tight spot, where there is perceptible resistance, that can be easily overcome with a little more force. This is an older, well worn, revolver that I have a lot of parts for that I am learning with, so no big deal if I make a mistake or if it takes a while to figure out. I do have the Kuhnhausen book. Much appreciation for your suggestions.

 

[armorer951]

Since the action has been ruled out as the cause of this abnormality you can place the blame on one or more of the remaining areas that frequently cause this type of resistance. Keep in mind this is a list of the most likely causes, not all of the possibilities are listed.

Misalignment of the yoke barrel

Excessive runout on the extractor rod. This is not caused by a bend the rod itself, but is caused by misalignment at the threaded interface joining the extractor and the extractor rod. (This one can usually be ruled out by testing rotation after removal of the front locking bolt)

Improper contact or improper fitting of the interface between the end of the extractor rod and the front locking bolt. Free cylinder rotation can also be impeded at this location by extractor rod runout and excessive end shake.

Tight or damaged cavities inside the yoke barrel and/or the yoke shoulder. Both of these cavities may need reaming to remove machine damage or irregularities, and correct size abnormalities. Both of these areas should be checked with the proper size reamer to insure they are clean, concentric, and of the proper size. Yoke barrel interior: .312" , Yoke shoulder: .250". (reamer will need to be slightly undersized)



Carter