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what causes cylinder notch drag marks?

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I have an Uberti Walker and noticed "hair-line" drag marks on the cylinder, like something is scratching the cylinder as it turns from notch to notch. So far I only notice it on two of the notches. What causes this and how do I prevent it?
 
The cylinder bolt stop is out of time. It is engaging too soon. This could mean a new cylinder bolt stop to be refitted or re timed to get it to engage closer to the next notch. This would be something a good gunsmith can help you with. I have the same problem on my ASM Colt Walker. It won't effect the accuracy. A lot of revolvers will do this. Since it is only happening on a couple of chambers, it means your cylinder is slightly out of concentricity.

HH 60
 
I wouldn't worry about it, that's very common on all revolvers. The locking bolt is set up to pop up early, before the cylinder notch actually aligns. That assures it won't skip the notch when cocked and fired rapidly. Better too soon than too late.
 
There are 4 clicks in drawing back the hammer on a Colt. The bolt is supposed to drop as the hammer is pulled back- to let the cylinder rotate. This bolt has a split tail, one side of this tail bears against an angled stub on the hammer that acts like a cam. As the hammer is continued to be pulled back the tail eventually slides off this cam and that allows the bolt to pop up. Ideally the bolt pops up into the leade- the dished out impression just before the actual notch. Very often however the bolt pops up much earlier and then drags across the cylinder- making the line you spoke about. As others have said it really doesn't cause any harm. Just make sure the bolt pops into the notch just at the instant the hammer comes to full cock. Or just slightly before but not so early that you have to keep moving the hammer back much more than about 3/16" from the bolt locking to the hammer going into full cock. Once in a blue moon you can have a situation where the hammer cocks BEFORE the bolt is in its notch- that's why I mentioned it.
 
hawken hunter 60 said:
Since it is only happening on a couple of chambers, it means your cylinder is slightly out of concentricity.

HH 60

Very interesting. Between one set of notches the drag only occurs about 25% of the way, between the other set of notches it is 100%.
 
tdp76 said:
hawken hunter 60 said:
Since it is only happening on a couple of chambers, it means your cylinder is slightly out of concentricity.

HH 60

Very interesting. Between one set of notches the drag only occurs about 25% of the way, between the other set of notches it is 100%.


I can't tell without seeing your revolver but it seems as though you may have a slightly out of round cylinder. There again, I wouldn't worry too much about it. The chambers them selves may be on center with the arbor in the frame. That's the main thing. Having worked in a machine shop for 30+ years I know that everything is built with a certain amount of tolerance. That means there is no such thing as perfect. If the cylinder is made in two or more set ups, it is quite possible something is not 100% concentric or on center, but it is within the manufactures allowable amount of error. I'm sure that it will shoot just fine. Mine did. As far as preventing it, the only thing I could think of is try a different cylinder from the manufacturer. Maybe you can find one that is machined closer. Getting a new custom made cylinder would cost you more than you could imagine if you were to contract a shop to do it for you. The cylinder bolt could be refitted and adjusted to not drag the cylinder, But that too could cost you a few bucks. My experience there is that you would need to make a new one. Not an easy task.


HH 60
 
The drag mark between chambers could be when you draw back the hammer to turn the cylinder but have not backed out the bolt all the way. You end up scribing a line on the cylinder with the bolt as you turn the cylinder.
 
Exactly so. If one lowers the hammer between chambers the locking bolt will pop up against the cylinder surface. Then on cocking the revolver the hand will rotate the cylinder with the bolt dragging the whole time.
 
tdp76 said:
I have an Uberti Walker and noticed "hair-line" drag marks on the cylinder, like something is scratching the cylinder as it turns from notch to notch. So far I only notice it on two of the notches. What causes this and how do I prevent it?

Lock bolt is out of tune.

But there is always some marking as the blot drops just before it drops into the lock bolt recess in the cylinder. The originals are oval in shape with no lead in as the later Colts had. The later Colts (second model dragoon has them with a retangular bolt cut) should drop the bolt just at the beginning of this relief cut. With no relief the Walker bolt must drop on the cylinder just before the lock bolt recess.
HOWEVER. A SLIGHT radius and polish on the lock bolt face will stock the bolt from cutting into the cylinder.
If the cylinder is being marked all the way around it needs to be tuned and perhaps parts replaced to correct this.

Dan
 
You've received good answers from the others.

I was thinking that as your cylinder locking bolt is only contacting in two locations it can't be very far away from where it should be.

With this in mind you could remove the cylinder bolt and use a whetstone to grind off about .003-.006 worth of the upper surface of the area that engages the cylinder. That's about the thickness of 2 human hairs or two pieces of printer paper.
After removing the material use the stone to gently remove the sharp edges.

The reason for using a whetstone is the locking bolt is hardened so it cannot be filed.
If you don't have a whetstone you can buy a piece of 120 grit wet/dry black sandpaper at your local hardware store and lay it on a hard flat surface like a table to provide a backup support.

The trigger/bolt spring is a flat piece that is under the trigger guard. Install it with the longer leaf resting on the trigger when you put the gun back together.
 
If the screw securing the trigger/bolt spring is loosened slightly, then that should serve to lessen the upward pressure of the bolt and lighten the amount of contact it has with the cylinder.
That may negate the need to perform any other adjustments.
 
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