I had a discussion with a fellow shooter recently. He claimed that during shooting there are no power/energy in the direction of the cylinder due to gas ring system in the cylinder, ergo no peening from yoke and extractor star possible.

My question: is it possible that the endshake increases by normal usage?

Absolutely. How else would it increase - other than gun-butchery?

I've had two go back to the factory with endshake issues, a 27-2 and a 317-1. Both had over 5,000 rounds through them and neither was abused. Endshake was so bad on the 317-1 that the front of the cylinder would rub against the back of the barrel.

Mechanical parts do wear, but I suspect shooting has more effect on endshake than dry firing. The gun needs a slight amount of front/back clearance for the cylinder to turn. I suspect you get rearward thrust upon ignition, when the case expands and drives the cylinder back and there has to be forward force when the bullets engage the cylinder throats. It seems that the more endshake you have, the faster it progresses.

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"I also cook."

Yes, firing a revolver is what causes increased end shake. It doesn't just happen by magic or dry firing.

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VCDL, GOA, NRA

I am aware of it but would love to have "scientific proof" so I can show it to him.

Don't bother apparently your friend knows everything already .

Scientific proof? How about, "For every action there is an equal and opposite reaction."? When a cartridge ignites, the case expands to temporarily grip the wall of the cylinder. The recoil force is transmitted to the cylinder, which is slammed backwards. Since there is already, and necessarily, a certain amount of fore-and-aft and side-to-side play built in to the system, the parts that hold the cylinder in place are slowly but progressively battered. Over time, the small tolerances built in to a new revolver thus get larger. Eventually, endshake and rotational alignment go out of whack and parts involved in controlling those aspects of operation must be replaced.

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Pisgah

Thank you! Now it makes sense, I didn't take friction into consideration. Always thought that the only thing which gets slammed is the casing itself.

Now can you still explain the peening of the yoke please?


Edit:
Does the cylinder also get pushed/slammed back when the gases exit the cylinder gap at the barrel end?

End shake on the cylinder is due to many factors, and is primarily the result of contact between the rear of the yoke cavity in the cylinder and the bearing surface located at the rear of the yoke barrel. A degree of "endshake" or gauge (.001" - .002") is built into the cylinder and yoke assembly, and is necessary for the revolver to open and close properly, and for the cylinder to rotate on the yoke as designed.

Almost all of the damage (and resulting excessive endshake on the cylinder and/or the yoke) caused at this location is the result of the impact of the bearing surface inside the cavity of the cylinder assembly and the rear facing end of the yoke barrel during recoil. Other incidental damage and wear here is causeD by dirt, shooting debris, improper or no lubrication, and the inevitable rotation of the cylinder assembly on the yoke from use....whether during dry firing or live firing.

During detonation, as the frame recoils rearward, the cylinder, which is free to move within the necessary gauge (space) provided to the cylinder assembly on the yoke barrel, moves forward, (remains static) and, along with the weight of the unfired ammunition in the cylinder (which also remains static as the recoil ocurrs) impacts the rear of the yoke barrel causing peening and wear. Forces from this "forward" movement of the cylinder during recoil are absorbed by the bearing surface at the rear end of the yoke bbl. Some of this forward pressure (or static pressure as the frame moves back) exerted on the yoke during firing is also exerted (transferred) onto the yoke stem and the yoke retension screw, which hold the yoke rearward.

When thinking about what's going on in there: It might be easier to understand this impact between the end of the yoke barrel and the end of the cylinder bore if you think about the yoke being a part of the frame and very forcibly moving back with recoil.....while the cylinder and it's weight of unfired contents (ammunition) stay "static" in the gauge the assembly has provided.....and subsequenty impact the yoke barrel as it moves back with the recoil force. Therefore.....wear and tear at these interfaces and contact points is inevitable from usage (live firing)......and the rotation of the cylinder during other movements, like dryfiring and opening/closing, for instance.

This normal wear and tear on the components can best be mitigated by keeping the cylinder assembly clean and properly lubricated, and by maintaining the proper gauge specifications within and between the assembled components.

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Ret LE, FA Instr, S&W Armorer

When the yoke is pushed backward on recoil as part of the frame, but the cylinder wants to stay stationary (static inertia) the back end of the yoke barrel gets hit by the internal part of the cylinder that bears against it. Every shot. That is how the end of the yoke gets peened and shortened. As mentioned above, the more endshake there is already, the faster it gets worse. It can only go so far because at some point the relative forward movement of the cylinder is stopped by the back of the barrel.

This happens on all revolvers, and is normal wear. At some point the endshake needs to be reset, often along with timing, etc. This is the same as a tuneup on a car engine. It's normal maintenance that needs to get done once in a while.

Edit - armorer951 was writing at the same time. I think we are both saying the same thing.

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Protocall Design

"I am aware of it but would love to have "scientific proof" so I can show it to him."

Easy. Take his favorite (newish) revolver, the larger the caliber the better, and measure the yoke barrel length. Fire 10000 full power rounds through it quickly and re-measure. Bet it will be shorter.

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Alan
SWCA 2023, SWHF 220

perfect, this is what I was looking for, cheers!

Is there also peening on the extractor star or only on the yoke due to the force?

Contact between the frame and the extractor is limited to the extractor boss located on the face of the extractor around the hole provided for the center pin. There is contact here, but no peening between the breechface and the extractor boss.

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Ret LE, FA Instr, S&W Armorer

Not wanting to get into any spurious engineering arguments here but I’ve listened to this discussion from several serious S&W experts including Jimmy Clark, Ron Power etc Since the early 80’s and much of what has been said is accurate. But let’s take the ‘ L ‘ frame and why it was built. It’s premise was essentially to (1) find a stronger platform for the high pressure 357 that was basically beating up and stretching the ‘ K ‘ frame, and (2) maintain a like or similar grip profile and dimensions for the average hand. Why because the ‘ K ‘ was stretching and as a result creating end shake and yoke issues beyond reasonable.

The days of low pressure 38 specials was over. Remember the S&W frame has a big side plate for access to the lock works. That is a lot of frame material, i.e. rigidity, removed in exchange for access. Frame stretching is a known condition among the industry but is normally only an issue with some frame and cartridge combos.

Rick

When I attended the armorer class, one of the tips that the instructor gave us if we stretched the yoke to much (correcting cylinder end shake) and causing binding, was to give the top of the handle/frame some taps with a babbitt when cylinder was closed to simulate recoil.

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Hello darknes my old friend

I have a 686-6 that has over 12,000 of mid upper to full magnum loads through it and has no noticeable end shake that I can tell since it was new.

Everything mechanical wears guns are no different. More use = more wear... even gears running in a oil bath will wear over time.

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Randy

What you say is very true and almost without exception but problems associated with deformation of an engineered product during service usually indicate a materials or design flaw. Not always, but in this case it was an older design being overtaken by a significant pressure increase of newer hotter cartridges.

Rick