fitting replacement cylinder

Jim Sharp

Jim Sharp

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Sadly, I bulged a chamber in the cylinder of my favorite S&W revolver (29-4) and purchased a "gently used" replacement on line. I've read here and elsewhere that such a replacement often drops in without special fitting, so . . .

Fingers crossed, I installed the new cylinder and extractor as-is to see what would happen. Timing is spot on and both headspace and b/c gap are good. Ejector rod is straight and tight. The replacement cylinder closes a little hard and both single and double action are stiff with some drag but aside from feeling stiff and heavy everything seems to work okay.

I thought maybe installing the original extractor in the replacement cylinder would solve the issue, but it doesn't fit because the indexing holes don't line up - an unexpected surprise. Not sure what to look at next. What am I missing? What steps would a gunsmith follow? Just curious and trying to learn as I go, and definitely not attempting to do any "shade tree gunsmithing".

Thanks in advance
 
Check the fit of the front locking lug with the end of the extractor rod. Resistance here from run out or too tight a fit can cause unnecessary drag.

Also, you'll need some gauge or "space" in the cylinder assembly for everything to work as designed. This space is sometimes called "end shake", and is required for proper function. About .001" - .002" of gauge between the end of the yoke barrel and the rear of the yoke cavity in the cylinder allows the cylinder to spin freely when closed. Material can be removed in small (tiny) stages until the needed space is achieved. Best tool for this is a yoke facing cutter.

With the cylinder closed, you should be able to detect a bit of front to back movement of the cylinder. If it's too tight, (no movement at all) needed space can be achieved by removing a bit of material from the end of the yoke barrel. Be sure to eliminate other possible causes prior to removing material here. Obviously, you can't put it back on after it's removed.

Other possible causes for poor cylinder rotation and binding from another thread:

Is the extractor rod out of alignment? (straighten, remove run-out)

Is the front locking bolt imposing too much tension at the end of the extractor rod?

Is the yoke aligned properly?

Does the hole through the yoke shoulder fully accommodate the extractor rod without undue contact during cylinder rotation? (open diameter slightly if necessary)

On older style guns, is the yoke button properly fit to the yoke screw?

Is the B/C gap correct? (is the cylinder dragging on the barrel extension?)

Is there excessive end shake?

(BTW, these are the most common problems, but is not even close to an all-inclusive list.)



After eliminating all of the above possibilities that can contribute to cylinder binding or poor cylinder rotation.......to check for yoke barrel and yoke cavity contact (and resulting drag and resistance to free rotation), you can clean the yoke bearing surface at it's end and place some black Sharpie or Dykem on the end of the yoke barrel. Re-install and cycle the action after installing the yoke screw. Contact during this test cycling will rub off your mark made with the Sharpie.
 
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It sounds like the cylinder may be a little long on the crane. First, use a toothbrush to clean really well under the extractor and on it's seat in the cylinder. Try it again. If still tight, you may need to trim a little off the back face of the crane tube. There is a special piloted cutter for this, so may need to take it to a revo smith that has the tool.

Edit - armorer951 beat me to it with a more detailed answer.
 
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I put sharpie on the end of the yoke barrel and spun it to see where it rubbed and then gently filed the rub spots until I got the endshake I was looking for. It doesn’t take much and you want to keep everything even so it wears better
 
Dieselteck56, and Amour I do the same thing only using Prussian blue. You can also use the cutter from a care trimmer and a pilot that just fits inside tube. But the die method will show you thee high spots and it usually doesn't take much.
 
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The most common cause presuming you are using the original extractor rod and cyl center pin:

Close cyl with a credit card between cyl and frame window to hold the cyl locking bolt down in the frame.

Turn cyl by hand and feel for drag.

Now open cyl, remove extractor rod and center pin, then close cyl and push cyl release thumbpiece forward. Check for drag. If the drag is lessened, the problem is an extractor rod that's too long.

Remove the extractor star and remove a slight amount of the front end of the star where the rod threads into it. Install ext rod, close cyl with credit card in place and recheck for drag.

Extractor star:

You posted that you checked the headspace and it's good. But how about the extractor star against the breach face. Put ink on the star and check it for rubbing against the breech face by turning the cyl by hand.
 
The credit card trick must be a Colt revolver thing. Trying as hard as I'm able, but I can't get a .030" credit card under the cylinder in any of my S&W revolvers. Available space in that window in my old model 19 turns out to be about .006".

I guess I'm stuck with simply holding the hammer back to the location where the cylinder stop drops down out of the way to diagnose cylinder rotation resistance.:D I'm totally clueless.
 
Thank you, thank you, thank you! I need to get to work on these ideas but it'll be a couple of days until I'm able. In the mean time I have plenty of food for thought.

There's such an unbelievable wealth of knowledge here - an embarrassment of riches, as it were. I suspect some others will also profit from the answers given to me. Again, my thanks to all.
 
armorer951 said:
The credit card trick must be a Colt revolver thing. Trying as hard as I'm able, but I can't get a .030" credit card under the cylinder in any of my S&W revolvers. Available space in that window in my old model 19 turns out to be about .006".

I guess I'm stuck with simply holding the hammer back to the location where the cylinder stop drops down out of the way to diagnose cylinder rotation resistance.:D I'm totally clueless.
Click to expand...

Yes some cards are too thick. But it doesn't take much to hold the cyl lock down. A business card works very well.
 
When I am fitting a cylinder I always have feeler gauges handy and they slide right in there. Another thing I have on my bench is some 309 stainless foil. I got it to make packets to HT stainless knife blades to keep out oxygen, but it is also great for other stuff. A piece of it will protect against file marks way better and tougher than any tape or aluminum foil. Under cylinder to hold stop down, Above barrel extension to file for final fit. You can slide it where you want it and fold it around so it stays put.
 
I have the impression that Armourer951 knows a thing or two about revolvers. Wow. That said, I believe this suggestion by Hondo44 is what made the difference in my case:

Hondo44 said:
But how about the extractor star against the breach face. Put ink on the star and check it for rubbing against the breech face by turning the cyl by hand.
Click to expand...

After judiciously filing a small amount from the face of the extractor star then using a stone to polish away any burrs or file marks (and also after checking everything suggested by everyone else) I reassembled my gun, and much to my delight, it now functions flawlessly.
 
Have you had an opportunity to check your rear gauge or "headspace" since making the changes? Just wondering if it still falls in the acceptable range.

For future reference, if and when increased gauge is determined to be needed to accommodate the parts in the cylinder assembly, or to relieve "binding" evident in the cylinder rotation, the correct place to remove material is from the end of the yoke barrel, and not the boss on the extractor. The surface of the boss on the extractor is only .008" to .010" above the ratchet teeth, and is the rotational bearing surface between the extractor/cylinder assembly and the breechface.

The other issue is that while the barrel of the yoke can be stretched or shimmed to increase it's length, the extractor boss cannot be lengthened. Alterations here (removal of material) can render the extractor assembly unusable.
 
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Thanks armorer. This, of course, makes perfect sense to the left side of my brain. Headspace is still okay but not by much. I could easily have gone too far since I didn't have your insight, but I didn't and I'm grateful. I just need a bigger hammer . . .
 
I personally prefer my headspace (rear gauge) to be closer to max than minimum. If near min a bit of crud under star or a rim or a just slightly high primer will cause drag or bind, where closer to max gauge will not. Also case head thickness can vary a bit.

There is a fix for tight gauge without replacing extractor though. If I had a cylinder without enough gauge for case heads to always clear I would consider using a reamer to recess the chambers enough to have correct gauge.

My 455 triple lock came to me reamed with the rims partially recessed so that the thicker 45 colt rims would clearance.

Fitting new pin alignment style stars sucks because not only did S&W vary the location of where they put the pins, I believe star and cylinder were match drilled as a set. You can take 2 cylinders of same vintage and the stars will go until the hit the pins then hit pins. I have never had one work right yet. The new style stars with the odd arm ends seem to be able to go from one to the other though.
 
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