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Old 01-02-2018, 09:01 PM
JayFramer JayFramer is offline
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Default Endshake Help!

Hey gang! I've got a pre-lock 64-5 and it has a tiny, very small amount of endshake. Barrel/cylinder gap is .006", Lockup and timing are perfectly fine but with the trigger held to the rear, there is a tiny perceivable amount of front and back play to the cylinder.

My questions:

A: Is this normal for a Model 64?

B: How does one measure endshake?

C: Are there "specs" for permissible endshake in a S&W Model 64 K-frame .38 special revolver?

D: If there should be absolutely 0 endshake, how do I go about correcting the issue? Is it user correctable or will I have to send it back to the Mothership?

Guys I am freaking the hell out over here, not sure what to do!! I also want to get some target grips for it but not if it'll shake itself to pieces in short order.

Please help!!
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Old 01-02-2018, 09:09 PM
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Here is a link to a thread I had bookmarked in the past that talks about endshake and how to measure it.

<<<LINK TO THREAD>>>
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Old 01-02-2018, 09:24 PM
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Absolute zero endshake can be a bad thing, as it can cause binding. .001-.002 would be considered right about where you want it. .004 marginal and .005 would be the area where people consider doing something about it. With a 38 spl, .005 or even .006 is no great cause for alarm, though. Use a feeler gauge to measure the difference between barrel/cylinder gap with the cylinder pushed forward, and again with the cylinder pushed back. You can take up the slop by adding an endshake bearing.

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Old 01-03-2018, 02:09 AM
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If you find you have more than .002" endshake I'd suggest you install a cylinder bearing (shim/spacer), commonly in .002" thickness, for the yoke's barrel face to eliminate the play.

That gap will only get bigger from the cylinder's recoil pounding it if you don't.

Ex: If you have .004" barrel gap & .003" endshake before and you install a .002" bearing you'll end up with .006" barrel gap & .001" endshake, which is ideal.

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Old 01-03-2018, 03:30 AM
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Thank you all so much. It is right at .003" endshake, measured with your instruction.

What do you all suppose I do? Also, as an aside the single-action pull is very very light. I don't have a trigger pull weight but I'm guessing a pound or so? There is no push-off even with a good bit of pressure on the back of the hammer when cocked.
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Old 01-03-2018, 04:53 AM
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You can replace the trigger rebound spring with a stiffer one. That will add weight to your trigger pull.
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Old 01-03-2018, 07:51 AM
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Quote:
Originally Posted by JayFramer View Post
Thank you all so much. It is right at .003" endshake, measured with your instruction.

What do you all suppose I do? Also, as an aside the single-action pull is very very light. I don't have a trigger pull weight but I'm guessing a pound or so? There is no push-off even with a good bit of pressure on the back of the hammer when cocked.
Some end-shake is not only normal - but needed for proper functioning. I'd say .003" is about the most I'd allow without a correction - but if it were mine I'd leave it alone for the time being and correct it if and when it moves to .004".


Shims are available from Ron Power and they come in .001" and .002" versions. You can stack them when necessary to achieve the correction you want. Just bear in mind when you correct the end shake you will also be increasing B/C Gap.
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Old 01-03-2018, 08:38 AM
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The critical measurements are the rear gauge or headspace, whch should be .060" - .064".....and the front gauge or barrel/cylinder gap, which should measure .004" - .010".
As others have said, some end shake in the cylinder/yoke assembly is "normal" and necessary both to allow the cylinder to rotate propery, and to accomodate lubricants and filth.
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Last edited by armorer951; 01-03-2018 at 08:45 AM.
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Old 01-03-2018, 01:18 PM
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Many say that minimal endshake in a S&W revolver is normal and fine. Whether that is per factory spec or not, I'm not sure.

My personal opinion is revolvers should have ZERO endshake. Colts were factory spec'd for ZERO endshake. I expect my S&Ws to be the same.

Will a tiny bit of endshake (.001"/.002") ruin your gun quickly? Probably not, but I'm a firm believer that any endshake at all will just continue to get worse over time due to the back forth ability to peen.

Just my opinion.
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Old 01-03-2018, 02:33 PM
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To accommodate the moving parts in the assembly, some endshake, or gauge, is required. The term "zero endshake" is not possible in this particular moving assembly, because with no gauge or space between the components (cylinder and yoke barrel, and extractor boss and breechface) the cylinder would not turn, and it would be impossible to open and close the cylinder without a hammer. Further....lubricants, shooting debris, and environmental changes (temperture extremes) could also not be accommodated in such an assembly. We all know how passionate police officers are about keeping their sidearms properly cleaned and lubricated.....so they (we) have to make allowances for these folks too.

Ideally, when initially factory fit, or if new components are added, the headspace should be as close to the shortest rear spec as possible, in this case .060", and the front gauge should be fit to accomodate enough gauge in the cylinder assembly to allow for opening/closing and free rotation and still be on spec....or not less than .004". (service gun) Unfortunately, "ideal" specs are often not fully met on the factory floor when the assembly is fit.

As long as the front and rear gauges are correct, with the most critical being the rear gauge, and the yoke is fit properly (the required internal gauge or space is supplied), the revolver will function as designed.
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Last edited by armorer951; 01-04-2018 at 08:54 AM.
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Old 01-04-2018, 02:18 AM
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Quote:
Originally Posted by JayFramer View Post
It is right at .003" endshake, measured with your instruction. What do you all suppose I do?

Also, as an aside the single-action pull is very very light.
Install a .002" bearing you'll end up with .001" endshake, which is ideal.

Install a new factory strength trigger rebound spring & see how it feels before trying anything else.

Earlier you said "Barrel/cylinder gap is .006". So you actually had .003" B-C gap & .003" endshake then, right?

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Old 01-04-2018, 04:55 AM
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Quote:
Originally Posted by iPac View Post
Many say that minimal endshake in a S&W revolver is normal and fine. Whether that is per factory spec or not, I'm not sure.

My personal opinion is revolvers should have ZERO endshake. Colts were factory spec'd for ZERO endshake. I expect my S&Ws to be the same.

Will a tiny bit of endshake (.001"/.002") ruin your gun quickly? Probably not, but I'm a firm believer that any endshake at all will just continue to get worse over time due to the back forth ability to peen.

Just my opinion.
I look at End-shake as I look at high end 1911 Pistols.......

When you spend the big bucks for let's say an Ed Brown 1911 (just as an example and I am NOT picking on Ed Brown here) the pistol is fitted so tight and so precise that in the beginning they are usually unreliable, get jammed and have many FTF's. As the pistol wears in things loosen up and become more functional.

If a S&W Revolver had zero End-shake, the Cylinder would bind up and the Revolver would soon cease to function. We all know that it doesn't take too long for the rings of Lead, Carbon & dirt to build up on the Cylinder face and that would be just enough to clog up the works. Any moving parts on any machine that gets dirty so fast needs a tolerance to properly function. If it didn't, premature wear would take place as well. Excess is no good either - that's why there is a "sweet spot" or "range".

Last edited by chief38; 01-04-2018 at 04:56 AM.
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Old 01-04-2018, 07:18 AM
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Thank you all so much! I am learning a lot.

What is "rear gauge" and how to I properly take a measurement of said rear gauge?
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Old 01-04-2018, 08:26 AM
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Distance between the breechface and the rear of the cylinder..... insert feeler gauge into the area between the hammer nose bushing and the rear face of the cylinder.
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Last edited by armorer951; 01-04-2018 at 08:27 AM.
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Old 01-04-2018, 08:27 AM
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Rear gauge is the amount of room from the rear of the cylinder to the face of the recoil shield where the firing pin comes through. Get a set of automotive feeler gauges and using the thicker ones at first and then a thin one or two to find out how much space it is. This is for non recessed cylinders. Your typical rimmed pistol cartridge has a rim thickness of .060, this rim has to fit between cylinder and recoil shield of course. But if you have to much space (excess head space) here is what happens. Firing pin drives the cartridge all the way forward, it fires, now the case is recoiled back against the recoil shield. With excess head space the cartridge gets a run at the recoil shield. Kind of like holding your rifle an inch away from your shoulder. Not good.

With a recessed cylinder you can use a fired case and you should have no more than about .004 between it an recoil shield
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