why is cylinder gas ring stretching not a common practice?

[Whiterabbit]

Folks talk about cylinder shims all the time, but not so much using the swage tool to stretch the cylinder.

Ruger always leaves plenty of gas ring shank to use this tool.

So why don't we see revolvers on gunbroker more often with a swage ring on the cylinder? Given the frequent discussion on endshake, people do care enough about it to do something...

What's up?

[FergusonTO35]

Interesting, please explain how this works.

[Whiterabbit]

circular swage. by compressing around the "nub" at the front of the cylinder, material is displaced forward, lengthening the cylinder. you overshoot it a smidg,e then polish for a perfect fit. Zero backlash. Leaves a groove in the gas ring.

way more discussion about shims out there. than the swager.

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Here's a picture of a swaged cylinder. zero end play, still the rotational endplay from "whatever" (latch play in the latch window, latch play on the trigger pin, latch too small, etc etc etc etc. whatever). As long as you have a gas ring as long as the swage, it should work.

[Petrol & Powder]

I think you're talking about stretching the crane or the arbor that the cylinder rotates on, not the gas ring on the front of the cylinder.

The two accepted methods to reduce cylinder end play are: 1. remove the cylinder from the crane (yoke), place the required number of shims in the center bore and return the cylinder to the crane.
2. remove the cylinder from the crane, insert a mandrel into the center of the crane to prevent it from being crushed, use a swaging tool to "stretch" the crane a little too long and then carefully ream the end of the crane until the exact desired length is obtained.

Both methods accomplish the same result but the swaging process requires a few more tools. However it doesn't require shims and therefore there are no shims to become lost or damaged later.

Back in the days of police revolvers, the shim method was generally not accepted for duty guns with the theory being a shim or shims could become damaged and tie up the cylinder.

[Petrol & Powder]

Whiterabbit, I missed the point that you were talking about single action revolvers. I was addressing DA revolvers with swing out cylinders.

[paul h]

Honestly I've never heard much about the process. When I went about addressing the excessive end gap on my old model 357 I bored the cylinder to accept a press fit drill bushing and ground it to the correct length. Swaging certainly would have achieved the same thing, but it would have required me to get a specialized single use tool vs. a $10 bushing.

[DougGuy]

All it does is "fix" something that has never been much of a problem in the first place. Rugers are by design clearanced to be loose. They are made this way on purpose. When you fit a bigger base pin you take out the ability for the forcing cone to pull the cylinder into alignment with the bore as the boolit transitions from the cylinder throat into the bore. The cylinder NEEDS this amount of slack so it can align properly and the gun won't beat itself to pieces if you leave it as designed from the factory. Same with the bolt that locks the cylinder into rotational alignment. Yes you can shim the bolt and align the cylinder more perfectly than the factory did it, but again they NEED the ability for the parts to move so that energy absorbed during firing is spread throughout the gun instead of focused on a few critical areas after you tighten the gun up so there is less or no movement when it is locked up and ready to fire. Unless you line bore each chamber, it is pretty much a waste of time and money to take the movement out of a Ruger SA revolver.

What stretching the gas ring does is remove front to rear movement, or "end shake" as it's called, but it increases the barrel cylinder gap equal to the amount that you force the cylinder rearwards. This will allow more burning gases to exit the gap and erode the end of the barrel much quicker than a tighter gap would allow. So you "fix" the end shake, which by all accounts can shoot tens of thousands of rounds without being an issue, but you accelerate barrel erosion by widening the barrel cylinder gap.

The bottom line is this. Rugers are meant to be loose. This way they don't shoot themselves to pieces. You NEED to leave those tolerances in the components, the revolver will last many generations of one's family if you leave it alone.

There are only TWO things necessary for a Ruger SA revolver to shoot properly and accurately, these are cylinder throats of the CORRECT dimension for the boolits/bullets chosen, and the forcing cone cut smoothly and evenly and concentric to the bore.

Swapping in a Wolff 30oz trigger spring does not help the revolver shoot accurately, it helps the shooter not disturb the sights when they shoot the revolver.

[Outpost75]

First rule of gunsmithing is to cut only on the cheapest part!

Leave the cylinder alone.

Stretching crane arbor works, but can be done only once or twice and requires specialized tools. Crane end must be trued afterwards.

Shims are inexpensive, easy to install are not tool intensive, do not require cutting on crane or cylinder, and can be added or repeated. Best technical solution.

[paul h]

(sic)

There are only TWO things necessary for a Ruger SA revolver to shoot properly and accurately, these are cylinder throats of the CORRECT dimension for the boolits/bullets chosen, and the forcing cone cut smoothly and evenly and concentric to the bore.



I'll take a slight exception to that. Provide the barrel is not choked that is true, and perhaps newer Ruger SA's don't suffer barrel choke the way some of the older guns used to. But my old model 357 had trouble keeping shots on the edges of a paper plate at 25 yds due to barrel choke. After Taylor throating, groups shrunk down to 2-3".

As to end shake, again it depends on the gun and how bad. My old model had 0.005" end shake and the front of the frame window was not perpendicular to the axis of the cylinder pin so the cylinder so the front of the cylinder only bore against 20-30 degrees of the area it should have. Once I lapped that area perpendicular end shake increased to 0.007" which exceeded the barrel/cylinder gap. So I tightened up the end shake to 0.001" and set the barrel back to tighten up the barrel/cylinder gap to 0.002".

[44man]

Keep the pin, bushing and ratchet lubed. I have used STP forever and my SBH has exceeded 80,000 rounds, heavy rounds and I can not detect any end shake.

[apen]

What stretching the gas ring does is remove front to rear movement, or "end shake" as it's called, but it increases the barrel cylinder gap equal to the amount that you force the cylinder rearwards. This will allow more burning gases to exit the gap and erode the end of the barrel much quicker than a tighter gap would allow. So you "fix" the end shake, which by all accounts can shoot tens of thousands of rounds without being an issue, but you accelerate barrel erosion by widening the barrel cylinder gap.


I would think accuracy would be improved by shimming the front of the cylinder and having a constant set gap. You would lose overall velocity, but the cylinder gap would be pretty much the same. In a loose gun, the first shot might be with a BC gap of .003, the next .005 or what ever arbitrary number between .003-.007 (the "in spec" range) in an un shimmed gun. Wouldn't the cylinder placement (fore-aft) be kind of random in a factory gun with .004" slop? How much more barrel erosion could one expect with a set .007 BC gap vs a variable gap of .003-.007? How much more accuracy would be realized with a set, but wide BC gap... if any?

[44man]

It got me interested so I measured my old SBH. I can't quite get .0015" in front of the bushing and gap is .005". As hot as I have had this gun at IHMSA, I would not want less.

[DougGuy]

I would think accuracy would be improved by shimming the front of the cylinder and having a constant set gap. You would lose overall velocity, but the cylinder gap would be pretty much the same. In a loose gun, the first shot might be with a BC gap of .003, the next .005 or what ever arbitrary number between .003-.007 (the "in spec" range) in an un shimmed gun. Wouldn't the cylinder placement (fore-aft) be kind of random in a factory gun with .004" slop? How much more barrel erosion could one expect with a set .007 BC gap vs a variable gap of .003-.007? How much more accuracy would be realized with a set, but wide BC gap... if any?

Anything that you do to remove a variable will have an effect on groups. That much is a known fact with a Ruger revolver. This is why it is more important to have the cylinder throats all even with each other than what actual size they are (provided they are all at least bore diameter or greater). I think you could realize an improvement over a chrony with a shimmed or stretched gas ring which would likely improve groups but by how much? A night and day difference or a negligible and maybe not even noticed in group size or velocity difference?

This is one that you would just have to chrony shots fired with loads that have every charge weighed, boolits weighed, neck tension the same, pretty much all the variables removed, to have an honest A/B test of the benefit of removing the end shake. You could then do a before and after test with shims which would basically do what gas ring stretching will do.

I'm not saying there would be no improvement, my point is that the improvement may be too small to be significant, and now you have the end of the barrel more exposed to erosion than it would be with the end shake left in it and a somewhat smaller barrel cylinder gap, i.e. a "fix" for something that isn't really broken.

[Whiterabbit]

It got me interested so I measured my old SBH. I can't quite get .0015" in front of the bushing and gap is .005". As hot as I have had this gun at IHMSA, I would not want less.

I'd be happy with that. My vaquero, I could get the .005" feeler to go in. Now I have no doubts that my .0015 gauge would never even start. I tuned my BC gap for the experience, but now that I have done it once I wouldn't mind a BC gap <.01". .005 seems like just the right dimension.

[jrayborn]

I would think that when the revolver fires the cylinder is naturally pushed (by recoil and pressure) back against the frame quite forcefully. This to me negates the concern that shimming the front (which I do) opens the BC gap (which it certainly does). It is my opinion that the gap will always be at max when the revolver fires. Shimming to remove play removes the slamming of the cylinder into the frame, basically ends the running start. I can't see that shimming would have any effect at all on forcing cone erosion due to a wider gap, the gap will always be at max, it's got to be.

Of the smallish number of Ruger single actions I own, every one accepts a .002 shim so I would guess that Ruger has about that amount of clearance engineered into the design. Difficult to say with certainty of course, just what I have observed.

[Ballistics in Scotland]

I think more revolvers than used to, depend on hardening of the cylinder, and harder hardening at that. This may make it more difficult to do accurately than it used to be.

I think if the issue were as important as some think it, the manufacturers would make cylinders with a longer, easily pressed in bushing for the front of the cylinder.

[44man]

It is a little more complicated. A Ruger will have about .009" headspace. When fired the primer slams out that much, then the case moves back to re seat the primer. This absorbs a lot of slam. The rest is taken by the ratchet.
The primer going back and the case also, should force the cylinder forward. is it enough to counter cylinder recoil? Maybe not but using STP adds some cushion too.

[Whiterabbit]

I think if the issue were as important as some think it, the manufacturers would make cylinders with a longer, easily pressed in bushing for the front of the cylinder.

Can't argue with that logic. At least with respect to importance to offset the cost.

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So I think the question of "why not common" is pretty well answered. None of the responses answered this question specifically though:

"if we have concensus it is not needed, time consuming, requires expensive tooling, no down-range benefit.... Is there a specific harm? Assuming eliminating endplay does not cause cylinder hang-up and does not change cylinder/barrel alignment, then is anyone doing any other specific HARM by removing the endplay?"

Or is the consensus only​: "waste of time and money"?

[44man]

then is anyone doing any other specific HARM by removing the endplay?"
Not if it is too much. You need some for expansion so you can go too tight as with anything else on a revolver. Revolvers are funny animals with all the chambers not fixed.
The question is how did end shake get so bad that it needs shims?
I have heard of frame stretch on S&W's forever but with all I owned and worked on, I can't tell you it is true. I think it is wear mostly, dry guns. Clean after all shooting sessions and never lube properly. Gun oil is not really good enough. Some greases work but darn it chain saw chain oil can save your gun and so will RCBS case lube that I think is just STP.
The worst revolvers are fit so tight they destroy themselves fast. I won't go into it again, I hurt feelings.
My advise is to not fool with what is not wrong.

[Whiterabbit]

No hurt feelings here. What are the symptoms of a too-tight gun that destroyed itself? I assume we aren't talking catastrophic destruction, just a gun rendered inoperable. Like the pawl fracturing, the cylinder latch bending or getting peened so that it wont fit cylinder pockets, critical timing surfaces getting damaged, throwing the timing, etc.

But that's not DATA, that's just my imagination. Can you give me an example of, very specifically, what damage was sustained to a ruger fit too tight? Let me be clear: this is not a challenge, it is a request for the experience of others so that I can leverage that knowledge and know what signs to look for.

[44man]

No hurt feelings here. What are the symptoms of a too-tight gun that destroyed itself? I assume we aren't talking catastrophic destruction, just a gun rendered inoperable. Like the pawl fracturing, the cylinder latch bending or getting peened so that it wont fit cylinder pockets, critical timing surfaces getting damaged, throwing the timing, etc.

But that's not DATA, that's just my imagination. Can you give me an example of, very specifically, what damage was sustained to a ruger fit too tight? Let me be clear: this is not a challenge, it is a request for the experience of others so that I can leverage that knowledge and know what signs to look for.
Not a Ruger. A more expensive. Line bored that egg shaped throats, ate the forcing cone and rifling on one side. I have shot super accurate Jack Huntington Ruger conversions with more play then factory guns.
There is a myth that line boring is better but I will say Ruger does better with gang boring cylinders.
Some fit a Belt Mountain pin to a Ruger to stop the pin pulling and is OK but they fit so tight, the cylinder can't index to the boolit.155405This cylinder was reamed but see the black areas that the reamer never touched. That is off side wear from being too tight. Same on every throat. Line bored. You should see the cone and rifling.

[Whiterabbit]

OK, so the risk is the chambers no longer being in alignment because of being too tight causing wear to the throats, forcing cone, and barrel.

Assuming there is enough play remaining or alignment achieved, your concern is alleviated?

(I recognize that that assumption may be difficult or even impossible to achieve, but it's still a valid "what if" scenario)

[44man]

Well, I did say if end shake is excessive, you can remove some as long as you leave enough for heat expansion. So your question is valid.
I don't know what the tool looks like and if it uses a mandrel in the pin hole to keep from making it smaller so the pin should be made to fit like the factory made it. Even with a mandrel you could shrink it.
Gap never concerned me much but if too small, pressure escaping will be at a much higher pressure. Seems to me that would tend to cut steel worse.

[DougGuy]

To answer your last specific question, no I do not think there is HARM per se in fitting the cylinder end shake out, IF it doesn't open the b/c gap enough that you start getting erosion and flame cutting of the fire ring (the flat part at the end of the barrel that meets the cylinder face). Obviously this is brought on by burning powder gases escaping, so any widening of this gap would allow more burning powder gases to escape, this one is a no brainer, 2+2=4.

If you tighten an entire Ruger, it may last many generations and stay tight IF and ONLY IF the cylinder is align bored with the barrel at full lockup. Any misalignment in the cylinder throat will cause the forces of impact to start beating on the latch bolt under the cylinder, and also the pin that holds the latch bolt. This is where the gun will start to show wear faster. That's why it's better to leave the slack in a Ruger, as 44man said, it has it's own ways of absorbing and distributing the energy from firing.

There have been some big name 'smiths turn out some fantastic work on Ruger SA revolvers, I can think of reading a few gun rags in the 90s that featured some of these guns now and then, but they had done the entire job which included align boring, welding the window in the frame where the bolt latch sits, making a narrower bolt latch, and making a cylinder with smaller bolt cuppets. I am sure the lucky souls that own some of these gloat over them and rightfully so, but I fear most are safe queens and an article of pride in workmanship rather than everyday working guns.



This cylinder was reamed but see the black areas that the reamer never touched. That is off side wear from being too tight. Same on every throat. Line bored. You should see the cone and rifling.



Tell you something else that is quite common to do this, using a reamer that doesn't have an absolutely snug fitting bushing. Solid nose reamers are VERY likely to ream throats off center and the dark areas are areas that are NOT cut by the reamer's flutes. Usually this is from egg shaped throats but it can be from a reamer that fits too loosely in the throats as well allowing the tool to take a cut that is not centered in the chamber.

[Whiterabbit]

It's funny how I assumed it would be understood that addressing endshake would have to necessarily include:

Examine gas ring bearing surface
Examine ratchet bearing surface
Examine BC gap
Examine headspace

Since all are affected by using the tool. but I can definitely see how it might not be read that way. And certainly by any other hobbyist who might read this and not instinctively know these factors would be affected by adjusting endplay. Thanks for addressing it specifically.

[44man]

Tell you something else that is quite common to do this, using a reamer that doesn't have an absolutely snug fitting bushing. Solid nose reamers are VERY likely to ream throats off center and the dark areas are areas that are NOT cut by the reamer's flutes. Usually this is from egg shaped throats but it can be from a reamer that fits too loosely in the throats as well allowing the tool to take a cut that is not centered in the chamber.
True and I did use a good bushing and only cut after damage was done. Each throat had the wear in exactly the same spot. I also cut the forcing cone and brought the gun from 6" at 50 down to 1" groups.
He would not send the gun back since the factory wanted too much to repair it.
Damage was done by shooting factory loads since when the gun was new, throat slugs were round.
The .454 has a lot of side force when a bullet hits the barrel edge, it used to spit pretty bad.
But it worked out and he is happy, started to load for it and now uses cast.
I also eased off on the cylinder lock on the proper side to give it a little wiggle.