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Old June 3, 2005, 12:42 PM   #1
YosemiteSam357
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Cylinder Lock (revolver operation)

On a typical S&W type revolver, is the only mechanism responsible for positive cylinder lockup (aligning the cylinder bore to the barrel) the cyl. lock pawl above the trigger? This appears to be the case but I wanted to ask those more experienced.

So does this mean if you start getting sloppy lockup (cyl. can rotate some amount when hammer and trigger held back) the only thing that can be done to correct is to get a wider pawl, or a new cylinder with sharper stop slots in it? There's nothing that can be done to the ratchet or the hand to tighten it up?

Finally, how much rotation is considered bad? I've got a couple of older revos that'll allow some deflection, not enough to cause timing issues, but more movement than (for instance) my friend's brand new 629, which locks up like a vault (no rotational movement or endplay/shake -- none).

Thanks in advance,

-- Sam
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Old June 3, 2005, 02:02 PM   #2
Dfariswheel
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First, like all modern revolvers, the S&W is INTENDED to have some cylinder looseness at the moment of ignition.
The only revolvers to lock tightly when the trigger is held back, are the older design Colt revolvers, like the Python.

The looseness in the cylinder at ignition is to allow the cylinder to align itself with the bore.
The old Colt guns, with their "Bank Vault" lockup are perfectly aligned with the bore at ignition. This means the bullet enters the bore perfectly aligned, and with no distortion.
The down side is, the Colt MUST be in absolutely perfect adjustment, or the gun just fails to work properly.

Gun like the S&W, Ruger, and Taurus allow the bullet passing into the bore to align the cylinder's chamber with the bore.
The upside of this is, the gun doesn't have to be in perfect adjustment, if it's worn slightly it still works acceptably, and it's cheaper to build.

The down side is, since the bullet never enters the bore perfectly, it gets distorted, degrading accuracy.

This is why the older Colt revolver design was famous for having better accuracy on average, than any other brand.

If a S&W develops too much cylinder looseness due to a worn locking bolt, it's fairly easy for a qualified pistolsmith to fit a new, oversized bolt.

Misalignment, or a "loose" cylinder can be caused by other things than the locking bolt, but this is the main one.

Again, in order to work properly, a S&W must have some rotational play in the cylinder at the moment of ignition.

There is no standard on "how much it too much".
The test for problems is an accuracy test off the sandbags.
If the cylinder "seems to be" too loose, AND the gun is inaccurate, it needs repair.

If the cylinder "seems to be too loose" and the gun targets well, and doesn't exhibit other problems like spitting lead, it's good to go.
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Old June 3, 2005, 04:22 PM   #3
YosemiteSam357
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Thanks for the detailed explaination. Is what you refer to as the "locking bolt" what I called the "cylinder lock pawl"? (I'm sure it is, I just want to verify the terminology. Between "lock-up", "locking up", cylinder "lock" vs "latch", etc, these terms get overlayed waaaay to much.)

-- Sam

P.S. This is great information. I've read too much into "solid lock-up" on other threads, and assumed that any rotation was a bad thing. While I realized the difference between Colt and S&W in this regard, it never struck home that a little wiggle was necessary.
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Old June 3, 2005, 07:53 PM   #4
Dfariswheel
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The two main parts that determine lockup and cylinder rotation are known by different terms, depending on the maker.

The two parts are the small stud in the bottom of the frame window that actually lock the cylinder, and the lever in the recoil shield that pushes the cylinder around.

Colt calls these the Bolt, and the Hand.
S&W calls them the Cylinder Stop, and the Hand.
Ruger calls them the Cylinder Latch, and the Pawl.

Since I worked mostly with Colt's, I tend to use Colt terminology.
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Old June 4, 2005, 12:54 AM   #5
YosemiteSam357
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Got it. Thanks again!

-- Sam
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Old June 4, 2005, 02:16 AM   #6
BillCA
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Sam,

Quote:
So does this mean if you start getting sloppy lockup (cyl. can rotate some amount when hammer and trigger held back)...
Instead of holding both back, dry fire the gun and keep the trigger all the way to the rear. At this point (moment of ignition) my new S&W's exhibit almost no movement. You can detect some movement -- just enough to see/feel a little motion -- but this is probably due to the inherent tolerances needed to let parts work smoothly. Luckily, even my old M31 shows this same trait - tight lockup with the trigger all the way back and the hammer down.

With the gun "at rest" the "play" is somewhat more pronounced.
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Old June 4, 2005, 01:52 PM   #7
cntryboy1289
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Bill is on the right track

The S&W revolver should be lined up and firm when the hammer falls. I would check to see if it is tight at this time. If it moves, there are numerous things that can cause the cylinder to not be locked up at the time of firing. Check to see if the gun is locked up by trying to rotate the cylinder after firing. If it doesn't moves, you most likely are fine. If it does move, you need to have the gun timed correctly or you may just need to make the gun sing. Both of these involve the fitting of the hand and its relationship to the ratchet pads as well as the action and timing of the bolt. The gun may need to be ranged if you find that it leaves a heavy lead deposit on one side of the chamber

Have a smith check it out if after the hammer falls, you can rotate the cylinder in either direction. A really good book on revolvers will give you more information on the subject. Good luck.

The main difference in a Colt and the S&W is that S&W put the hand on the right side of the gun and it pushes the yolk away from lockup thus the gun gets out of range quite easlily. The folks at Colt put the hand on the correct side, the left, and it pushes the yolk into lockup and holds it there. This is where the Colt has the advantage over the S&W due to it having the more positive lockup causing it to be much more accurate than a S&W. The advantage of the S&W is that it can be worked on much easier than the Colt, the problem is that it has to be maintained much more often because of its design.
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Old June 4, 2005, 02:58 PM   #8
Unclenick
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The bolt almost always allows slight cylinder position slop in a revolver. When I bought my Redhawk, I was lucky in that there were 4 of them in stock at the time and I got to compare them to one another. I looked at three things:

First (after checking they were unloaded) I held each one up to the light and looked at the barrel-to-cylinder gap to see that the sides were parallel. I pushed the cylinders fore and aft in different rotational positions to see that it didn't contact the barrel or have an over-size gap.

Second, I operated them all single-action while dragging my thumb lightly on the cylinder. In one case the cylinder didn't lock up for every chamber. I rejected that one.

Third, I tore a strip off a business card and slid it in between the cylinder and the recoil plate of the frame. I then looked down the barrel and tipped the card fragment enough to get light bouncing off it. I wiggled the cylinder of each candidate alternately clockwise and counterclockwise to see how well the mean positions of the chambers were centered in the barrel and to see how much movement there was? One gun stood out as best. The others all could center at one extreme of rotation or the other, but this one's average position was centered. I checked to verify this was true for all chambers; then it came home with me for some trigger work.

With a scope and sandbags, shooting plain-Jane American Eagle 240 grain soft point loads, that gun shoots 1.25" groups of six at 50 yards all day long. Some days it pays to be a nit picker.

Nick
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Old June 5, 2005, 07:50 PM   #9
Dave Sample
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Intersting terminolgy among various makers. Rugerspeak, S&Wspeak and Coltspeak all call the same part by a different name. Why is that? Don't ask me! I like Coltspeak the best.
The hand/pawl turns the clyinder either clockwise or counter-clockwise.
The bolt/cylinder stop locks the clinder in place while the gun is being fired. The amount of play is not important unless the gun is not very accurate and they all have some play as they need it to function right. How much is too much depends on many factors. There are alway tolerances on handguns that give them leeway to work or not work. Without a gun in the hands of a pistolsmith, I don't know how you could tell what is acceptable and what is not. My theory is that they need to be tight when the hammer is back all the way.
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Old June 5, 2005, 10:00 PM   #10
cntryboy1289
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I agree mr Sample

If the cylinder isn't indexed up correctly, then it won't be tight. If it is, then there shouldn't be any play, otherwise, the gun isn't ranged correctly and will be shaving lead.
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Old June 6, 2005, 12:03 AM   #11
Dave Sample
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Shaving lead comes from the chambers being out of line with the forcing cone. This is why we check them with a Range Rod. If they are not dead nuts on, then we have to adjust the Bolt on a Colt by shaving down one side or the other. I am talking about the 1873 SA types, of course. Excessive end shake could result in spitting, also.
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Old June 12, 2005, 02:40 PM   #12
Harry Bonar
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cyl. lock.

Dear Unclenick:
Maybe we're both off, but I check revolvers EXACTLY the way you do! Isn't it funny that there is so much variance in revolvers. I like the "thumb pressure - slight" in testing lock-up! Good show!
I always take a pen-light with me on gun trading trips to check this alignment of cyl to bore; Dave uses a range rod which is the correct way.
The Rugers are the easiest to correct, I think - the Smiths' and Colt revolvers the worst.
S&W are the prettiest rovolvers ever made and if they just had a foreward lock-up they would be great, like the old tripple=locks!
I've got a Ruger Blackhawk, a 454 Super, a 44 mag redhawk and a nice 41 mag redhawk.
I like the Taurus revolvers, my mod 44, 44mag was a test gun from Wily Clapp, it locks very well even after his gun-test!
We all love guns and dogs! Harry B.
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