Hi,
I recently bought a 66-2 revolver online with a 2.5" barrel. When I got it home I noticed that the barrel cylinder gap was on average about 0.002". The end shake is about the same. The gap is maybe a touch bigger than 0.002" on 3 of the chambers and a touch smaller on the other 3. I ran several types of loads at the range today from factory FMJ to wadcutters. Predictably it did not take too long for it to jam, particularly on the 3 tightest chambers. Wiping off with a rag would restore it for another cylinder's worth, but then with wadcutters it jammed much faster. Anyway, none of this is surprising with a tiny gap. The question I have is first what can I do myself to make the b/c gap a little bigger, by a mil or so. Given the short barrel I can see the value of a small gap, but this is too small; I can't clean the gun every 5 min at the range.

Reduce the barrel extension length. The factory service people and assemblers do that with a file. However that's why it is predictably not always the same on each cylinder. There is a tool available though a bit pricey through Brownells that will allow you to trim the barrel extension with a true flat cutter. It is also used to recut the barrel forcing cone to a couple of different angles and includes laps to polish the cone after cutting. You might find someone on the forum that would loan you one if you ask who has one.

Would simply polishing the face of the cylinder help? Particularly on the fronts of the 3 tightest chambers...

So are you saying that if you correct the end shake you will have a gap of .004? That would seem the first step, correct the endshake with a bearing.

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Science plus Art

No no no sorry bad idea. Get the tool from brownells or get it to a good revolver smith( hard to find ) or back to factory. Do not mess with cylinder, you will wreck it.

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A republic if you can keep it

The first thing to do is correct the end shake issue and then worry about the barrel-cylinder gap.

The B-C gap was correct when the gun left the factory, the only thing that reduces it (short of deliberate gunsmithing) is development of end shake that lets the cylinder move forward! DO NOT TOUCH THE BARREL!!! S&Ws are a fairly simple mechanism, but they are very easy to screw up beyond repair if you do not know what you are doing and start filing on things.

I was thinking about that too, but shouldn't there be some amount of end shake? Just to be clear if I push back the cylinder I get a measurement in the gap of 4 to 5 mils, and without touching the cylinder I get 2 mils or less, so as I understand it, that's an end shake of 2 to 3 mils. Is that correct? A 2 mil cylinder bearing would give me an end shake of 1 mil or less; is that ok or will I create a new problem for myself?

Barring something else wrong, that would end the issue.
Some square the tube up to get essentially zero endshake with selected bearings, but I prefer about .0005 for an IDPA revolver. Anything down to zero (no preload) is fine for most purposes.
Anything over .001 is excessive.

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Science plus Art

What^^^^^^^ said.

End shake should be imperceptable without binding. Anything over .001" is excessive.

2 mil bearings ordered from Midway, thanks for the advice

Triggershims.com

in Michigan, cheap, fast service, comes in a regular mail envelope.

Good Place!

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NRA Pistol/Rifle Inst. RSO

So after installing the 2mil shim the endshake went to a lower level than I can measure and the b/c gap opened up to between 2 and 4 mils depending on where measured. This allowed me to shoot about 50 rounds before seizing up again. So the face required some substantial cleaning with a brush. I used what I thought were aluminum brushes, but now realize were steel to clean off the face. Now I am concerned if I have ruined the cylinder! Does it take many sessions of brushing to round off the chamber edges, or might I have done it in one session of stupidity?

I doubt you did serious damage.

As for the cylinder washers, they need to be greased. If you didn't, disassemble the cylinder again, thoroughly clean out the hole in the cylinder, making sure to get the bottom clean, then grease the washers and reassemble.

Greasing might prevent the binding issue.
If your barrel-cylinder gap is 0.004" and fouling is causing it to bind, you might look at other issues.
As example dirty ammo, lead bullets that are soft and cause excessive fouling, etc.

To properly clean, make sure to use a Lewis Lead Remover Kit from Brownell's to thoroughly clean the barrels forcing cone. Even if you only shoot jacketed bullets use the Lewis tool to remove carbon and copper fouling.

Scrub the rear face of the barrel and the front of the cylinder with a brass toothbrush OR even better, buy a "lead-away" cloth which just wipes leading, carbon, and copper fouling off by lightly rubbing the area with the cloth.
DO NOT use on a blued gun, it also wipes bluing off.

Last, if all else fails and the gun just keeps sticking, then and only then consider having the rear of the barrel trimmed about 0.001".
That would give you a barrel-cylinder gap of 0.005" and if it still sticks, something else is wrong. See a gunsmith.

As above, the only good/right way to trim the rear of the barrel is a special flat face cutter tool that works down the barrel with a Tee handle rod.

Before having that done, clean the cylinder hole, grease the washers, and use a lead-away cloth to wipe all fouling from the face of the cylinder and the rear of the barrel.
Try some different ammo.

Thanks. Yes, I did grease the washer and the cylinder rotates freely. I was using FMJ ammo but it was cheap range ammo. I got new more precise feelers and the gap is 0.0025 to 0.0035 depending on the chamber. I think I am ok with wiping off the dirt after 50 rounds, I was more concerned about the cleaning of the cylinder face I did as I can see fine lines in the steel from the brush, though I cannot feel them with my finger (smooth to the touch). I ordered the Lewis Lead Remover it does seem like a better tool than just using chemicals.

doesn't anyone 'stretch' the upper crane leg anymore??? do that and set the cylinder back to where you want it to be at................no need to "cut" any barrel extension, unless you HAVE to "square things up" ........keep cutting the "extension" and if the cylinder crane leg continues to wear and moves forward and eventually you will get misfires from too large a gap in the rear ( recoil shield)........ a job worth doing , is doing "right"

clean the bore GOOD (Lewis Lead remover) if you are using soft bullets, and possibly open the forcing cone a tad...............

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dan
NRA Benefactor,PMA

Not being a gunsmith, how does one 'stretch' the upper crane leg? Is this something that can be done by someone at home or does this require a gunsmith?

with a special swaging tool, it looks kind of like a pipe cutter. I believe Brownells can help you out there. While you are at it, they also sell a cutting tool for squaring off the end of the crane.

There are various ways to stretch the yoke barrel, which is the tube on the yoke that fits into the cylinder.

One way is with the special tool that looks like a tubing cutter. The tool has a rounded wheel that won't cut into the metal, but rolls a groove in it to stretch the barrel.
Stretching is done on the enlarged area at the rear of the barrel and a hardened steel support stud is inserted into the barrel to prevent collapsing it.

The second method is to insert the hardened steel stud, then use a small hammer and a bench block to tap the enlarged area with rapid taps of the hammer as you rotate the barrel.
This also stretches the barrel and doesn't leave a groove in the barrel.

After stretching a piloted end cutter is used by hand to trim the end of the barrel to make it square with the barrel and to give minimum end shake.