What causes cylinder drag lines?

J

johnson184

Inactive
I'm just trying to learn how revolvers work... and I'm a little puzzled at what causes drag lines on revolvers. On my S&W 10-10, there are drag lines on the cylinder... but doesn't the "bolt?" at the bottom of the cylinder retract while the cylinder is rotation? Why is it somehow causing a scratch over time?
 
Simply put, it's because of the way the gun is made.

Also known as "timing", meaning the point in the movement cycle of the parts, what is in contact where, and when.

S&W times their DA revolvers a certain way, and the turn ring (drag mark) is actually a sign that things are working the way they were set up at the factory.

The same ring on a Colt revolver indicates a problem with the timing, because Colt sets up their guns differently.

The bolt on a S&W DA does rub on the cylinder, some distance before the bolt cut in the cylinder. This is to ensure the bolt is there to lock into the cylinder when the time comes, and over enough cycles does wear a ring in the bluing. The turn ring is not mechanically significant.

Colt sets up their guns so the bolt comes back up to meet the cylinder much closer to the bolt cut, and does not normally produce the turn ring from wear in the bluing.

There's more to it, of course, having to do with the details of how different makers time their guns, but that's the short version.
 
Howdy

Because double action revolvers have mechanisms very different than single action revolvers, the causes of drag lines varies with the two different types of revolvers.

With a traditional single action revolver, such as a Colt, a drag line or turn line on the cylinder indicates either the revolver was mishandled, or its timing is off.

Here are the interior parts of a Colt Single Action Army. Most of the replicas made by Uberti and Pietta work the same way. Sorry I will have to explain the action with the parts laid out this way because my X-Ray machine is down for repairs, so I cannot show you the parts inside the action.

interiorparts.jpg




The round part protruding up on the hammer is called the cam. When viewed from above it is round, but as you can see from the other photo, in profile it is a wedge. The part next to the cam is the bolt. Notice there are two hook like 'tails' on the end of the bolt. More about why there are two tails in a moment. When the parts are inside the gun, the tails on the bolt fit over the rounded top of the cam. The hand is the part with the spring on it. The round pin on the hand fits into the hole in the hammer just below the cam. The purpose of the hand is to rotate the cylinder. Inside the gun, the hand sits on the other side of the hammer, so if I had mounted the parts together you would not see most of the hand. The trigger should be obvious, as should the three cocking notches on the hammer.



interiorparts02.jpg


As the hammer is cocked, several things happen. The section with the cam and hand hole rotates up. So the hand begins to rise up to start to rotate the cylinder around. At the same time, as the cam rotates up it lifts the tails on the bolt, rotating the business end of the bolt down. Everything is very carefully designed so that as the hand starts to push the cylinder around, the bolt has rotated down enough to free the cylinder to rotate. As the hammer is cocked to the half cock position (the middle notch on the hammer) the tip of the trigger (the sear) pops into half cock notch. At this point if pressure is let up on the hammer, it will stay at the half cock position. This is the loading position. The bolt has been withdrawn, and the cylinder is free to rotate in one direction. This is when loading and unloading happen.

The mistake some shooters make is lowering the hammer down from the half cock position. More about that in a bit.

The proper thing to do is to bring the hammer all the way to full cock. As the hammer approaches the full cock position, the tails of the bolt slip off the cam, and the split trigger/bolt spring pops the bolt back up. As the hammer goes to full cock, the bolt pops into its locking slots on the cylinder, and the gun is ready to fire. The bolt has popped up, locking the cylinder in place.

Now we get to why there are two tails on the bolt. The bolt is made of spring steel. The tails can flex sideways. When the trigger is pulled, and the hammer starts to rotate down, the wedge shape of the cam pushes the nearest bolt tail to the side. The bolt spring keeps the bolt up, while the cam shoves the tail to the side. This keeps the bolt up, keeping the cylinder locked in battery as the hammer falls. At the last moment, as the hammer falls almost all the way, the rounded top edge of the cam clears the bolt tails, and the bent one pops back in position, ready to start the cycle again. But all that time, the bolt has remained up, locking the cylinder in battery.

OK, now we can talk about the mistake. Bringing the hammer to full cock, then lowering it, completes the cycle in slow motion. The cylinder has been rotated to the next chamber. The bolt tails pop back in place, and the bolt remains up, locking the cylinder in position. However, if one lowers the hammer from half cock, the bolt never recycles. Instead what happens is the bolt rises up and presses against the body of the cylinder, but the cylinder has only rotated halfway between chambers, so the bolt is pressing against the body of the cylinder. The cylinder is free to rotate in this condition, and any inadvertent rotation of the cylinder will cause the bolt to rub against the body of the cylinder, causing a rub line.

That's the deal with mishandling a Colt.

Now for the timing.

Let's look at the cylinder on this old Bisley Colt. Yes, it has a turn line, because a whole bunch of times since it was made in 1909 somebody lowered the hammer from half cock and the bolt rubbed against the cylinder, causing a turn line.

bisley03_zpsa2a15e70.jpg


But if you look carefully, you will see that there is a 'teardrop' shaped scoop just above each locking slot on the cylinder. I call those scoops the lead ins to the locking slots, for want of a better term. When a single action revolver of the Colt type is timed properly, the bolt will pop up as those lead ins are over the bolt. There is a fair amount of tolerance here. As the cylinder rotates past the bolt window in the bottom of the frame, the tails of the bolt will pop off the cam and the bolt will pop up and contact the cylinder in those lead ins. If the timing is off, the bolt may pop up earlier, and contact the cylinder on its full diameter. That will show up over time as scuff marks on the cylinder where the bolt is popping up. Correcting the timing, if it needs correcting, involves careful removal of a little bit of metal from the bolt tails. Too much and you have to start all over again with a new bolt.



Now, for something slightly different, let's look at a modern Ruger single action revolver with a transfer bar. Here is my old Blackhawk that I bought new in 1975. Yes it has a bit of a turn line. Completely normal with a New Model Ruger. Ruger changed the timing of these revolvers on purpose, so the bolt would pop up a little bit earlier. So it is completely normal to have a partial turn line on the cylinder of a New Model Ruger, just like you see in this photo. Or, you could call it six separate partial turn lines, each extending from the spot the bolt pops up to the locking slot. Every time you cock the hammer, the bolt pops up early, contacting the cylinder, and causing the bolt to rub against the cylinder as it rotates. Completely normal with a New Model Ruger.

BlackhawkConvertible02_zpsbaa04ed2.jpg





Finally, let's talk about double action revolvers.

With modern double action revolvers; Colt, S&W, Ruger, etc, it is completely normal to have a turn line on the cylinder. This is because they have swing out cylinders. I will explain why in a moment.

Here is the action of a S&W Model 10-5, but the action of any modern S&W revolver will be very similar. S&W calls the piece that locks the cylinder in place the cylinder stop instead of the bolt. It is the piece just in front of the trigger. If you look carefully you can see its spring at the lower right corner of the part. The business end of the cylinder stop is poking above the frame directly above the trigger. It is in its normal position, the spring is pushing it up. The bolt stop sits on a stud mounted in the frame. But the cylinder stop is a very clever piece. There is a slot, rather than a round hole in the cylinder stop, that pops over the stud in the frame. When the hammer is cocked, or the trigger pulled, the tab on the front of the trigger pivots the bolt stop down into the frame, freeing the cylinder to rotate. The slot is the really clever part. When the trigger is released, the tab on the trigger pushes the cylinder stop forward slightly, while at the same time the cylinder stop spring keeps shoving the cylinder stop up. What this means is that as the trigger returns forward, even though the cylinder stop slides forward slightly, it is still pressed up, keeping the cylinder locked in place. As the trigger completes its cycle forward, the cylinder stop pops back to its normal position. Very clever stuff.

Model%2010-5%2002_zpsfn7rwsdm.jpg




OK, so why is there a turn line?

It is because the cylinder stop is in the popped up position when the cylinder is opened up. Closing the cylinder will shove the cylinder stop down, but the spring will keep it pressing against the cylinder. Exactly where the cylinder stop is pressing against the cylinder will be totally random, but unless one takes extra special care and carefully lines up a cylinder locking slot with the bolt every time one closes the cylinder, the cylinder stop will be pressing against the cylinder, and any inadvertent rotation of the cylinder will cause the cylinder stop to rub against the cylinder.

While the mechanisms of Ruger and Colt double action revolvers are different than a S&W, the cylinder stop or bolt is still in the up position when the cylinder is closed. So any rotation of the cylinder will cause a rub line to start.

I have been shooting revolvers for a long time, and I only once heard of one shooter who was so compulsive he carefully lined up the cylinder on a double action revolver every time he closed it, so he would not get a turn line.
 
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The reason S&W, Ruger, Dan Wesson, and the later Colt's like the Mark III and later have cylinder drag lines is because very soon after the hammer is started back or the trigger is pulled the cylinder locking bolt or cylinder stop drops back onto the cylinder and "rides" the surface for most of it's rotation.

Note the very short leade in front of the locking notches.
This is to allow the locking bolt a smooth, positive entry into the locking notch.
It doesn't matter if you line a chamber up on these brands, the locking bolt rubbing on the cylinder will leave a line as part of normal designed operation.

In the old Colt action timing is far more critical and complicated.
When the Colt is operated the bolt is held away from the cylinder for most of it's rotation and only drops into the long leade in front of the actual cylinder locking notch.

This means that if you were an absolute fanatic and only shot the gun and made certain a chamber was lined up with the barrel when the cylinder was closed, there would be no line on the cylinder of a Colt at all except actually in the long leade.
It's closing the cylinder and rotating it to lock that causes the line on a Colt.

So, a cylinder line on most all DA revolvers shows the action is operating exactly like it was designed to do.

A cylinder line on an older Colt action indicates the gun has been used in the Real World by a normal human.
In the Real World, almost all guns will get a line on the cylinder sooner or later because real humans are using them.
 
Bolt timing can be adjusted. For target guns, cylinders are not to turn fast. The bolt can be timed slower to minimize the drag line. For duty and carry guns, cylinders can turn fast because of fast shooting. Slow bolt timing may miss the notch (throw by). So faster bolt timing is desired. It causes drag line though.

I don't mine drag line on the cylinder, just like l don't mine holster wear. It is character of a working gun. A testimony of not slagging off, and the courage of saying what it really is.

-TL
 
Take a small square stone and lightly...

stone the closest bolt edge to center-line of the barrel, as remove that corner.
This eliminatesthe drag marks.
 
Even the best fitted cylinder stop will leave drag marks on a S&W as the very knowledgeable and reputable Dfariswheel has already mentioned.

The ball, that is the part protruding through the frame window has to be fitted for each cylinder slot. Width, engagement, and height have to be set. The timing of the bolt is set by shortening the stop bevel for faster return. When the return is too fast, the action will freeze up and the stop is ruined.
 
Lightly stoning that bolt edge can reduce engraving, but can't eliminate the drag line entirely in & of itself.

I rejected two brand new Smiths years ago that came with a turn ring already engraved the entire circumference of their cylinders from overly sharp bolt stop edges.

Not just rub lines in the bluing, an actual groove in the steel.
Removing the sharp bolt cutting edge would avoid that, but friction wherever the bolt contacts the cylinder will eventually remove material.
Denis
 
I believe when you see a drag line on a revolver cylinder, the gun is working properly in general. Some revolvers develop the drag line rather quickly and other don't.

I purchased a S&W blued Mountain Gun (41 mag) that was supposed to be "new", but it had drag marks from people handling it at the dealer. It was a shooter for me, so no problem.
 
Great read, Driftwood! Drag lines on revolvers have always bothered me. It seems to me that if a manufacturer is going to design a cylinder to have a drag line, it would mill a small, polished channel in the cylinder and perhaps coat it with something hard and slick, and use something like a roller bearing as a cylinder stop so as not to mar the cylinder. Metal scraping against metal just bothers me.
 
I believe when you see a drag line on a revolver cylinder, the gun is working properly in general. Some revolvers develop the drag line rather quickly and other don't.
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So you are ignoring everything I said about traditional single action revolvers?

It seems to me that if a manufacturer is going to design a cylinder to have a drag line, it would mill a small, polished channel in the cylinder and perhaps coat it with something hard and slick, and use something like a roller bearing as a cylinder stop so as not to mar the cylinder. Metal scraping against metal just bothers me.
Click to expand...

Good grief, how much would that cost? Revolvers have been around a long time without needing such unnecessary, costly 'improvements'. A drag line may be unsightly, but it I have never heard of it affecting the function of the gun.
 
It does if its function is to appreciate.
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I have many, many revolvers. Many of them are older than me. Some are a whole lot older than me. I do not buy them to appreciate in value. Bad as it is, the stock market still pays off better in the long run than most old firearms.

It is of course nice to find an old revolver without a turn line. Not going to happen on a S&W, as mentioned earlier. The more pristine it is, the more it costs. Even my old Colts mostly have turn lines simply because they are so old and have been mishandled at some point.

I have never allowed the presence of a turn line, or other honest wear, deter me from purchasing an old firearm.
 
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