My amateur fumbling with Colt revolver timing

[Clark]

I paid $150 for Colt Police Positive double action 38 S&W revolver made in 1911.

It turns out that it does not lock up in double action.
It has a problem known as late bolt drop.

The bolt is that little piece of metal that pokes up out of the frame, goes into a slot in the cylinder, and locks the cylinder in place for firing. That way the firing chamber is concentric with the barrel.

The bolt has to get out of the slot so the cylinder can rotate.

The trigger pushes on the hand, that pushes on the rebound lever, that pivots away from the bolt tang, so the bolt tang is up on the rebound lever cam, so the bolt pivots out of the way.

In the pic, the bolt is green, and the rebound lever is blue.

But pull the trigger a little further and the hand pushes a little higher, that pushes a little further on the rebound lever, that rotates a little further away from the bolt tang, so the bolt tang falls off the cam. That allows the bolt spring to push the bolt into the cylinder slot again.

My problem is that the hand pushes on the cylinder, and it rotates so far before the bolt drops, that the slot has already passed by where the bolt head is going to be.

How to get the bolt to drop sooner?
One way is to file some material off the rebound lever cam.
It is tiny and hard to see up inside the revolver frame. I had the revolver upside down and was trying to see it work, when the hammer fell and took a chunk out of my finger.

I got it working when I pull the trigger slowly. I will just put it away for a while, and keep changing the band aids.

 

[dfariswheel]

The WRONG way is to file the rebound "triangle".
Unless the rebound, bolt, or other part has been altered, the "tail" of the bolt is gently bent away from the rebound to allow the bolt to drop sooner.

The old Colt action is the most complicated modern type DA revolver action of them all.
The action is very definitely not intuitive.
What appears to be happening is not what's happening. Alter one part to fix something here, and something unexpected happens over there.
Each part performs at least two totally separate functions.

The complexity and tiny working surfaces are why few gunsmiths are capable of working on them and doing it right.
Not really understanding the action, they start filing or stoning on parts hoping to hit on a fix and wind up ruining the gun.

My best advice is to buy the Jerry Kuhnhausen shop manual Volume One on the Colt revolvers.
This was written as a training aid for new gunsmiths and covers the design and how to adjust it in deep detail.

http://www.brownells.com/.aspx/pid=25720/Product/THE-COLT-DOUBLE-ACTION-REVOLVERS-A-SHOP-MANUAL

 

[Clark]

Kuhnhausen lists 3 problems with the bolt dropping late and suggested fixes:

1) Too much inward bend? Adjust bolt tang.
2) Cam bypass bevel long? Adjust bevel.
3) E/I cam not rounded? Slightly round front of cam.

And I am doing all three.

Here is a video of me bending the tang of the bolt.
http://www.youtube.com/watch?v=Wz-3mYamPlE

 

[dfariswheel]

The problem with the old Colt action is knowing WHICH of the repair options is the correct one, or which combination of them is correct.
This is just one of those things that require experience and close observation to decide on.

Unfortunately, with Colt's, especially old ones, a problem is in detecting any alteration some other repair attempt may have done.
It can drive you nuts trying to diagnose a problem, only to finally find that someone years ago altered something in a repair attempt.

With the Colt's it's common to find that one of the old "get it to work SOMEHOW" gunsmiths altered a number of parts to get the gun to function and now you have more than one problem part, which throws off any attempt to fit a new part or correct a problem.
Diagnosing and correcting these is why there aren't many Colt qualified pistolsmith's around.

Also unfortunately, this is the type of problem that can't be advised on over the internet. You just have to actually see the gun to figure out what's wrong.

 

[Clark]

I have fixed the timing, which brings up the next problem.

In double action, if I pull the trigger too fast, the bolt never goes in the slot.

The whole cylinder - crane assembly is loose as a goose.

 

[Old Fuff]

Be sure the crane isn't sprung. Close and latch the cylinder, and then while looking at the frame/crane from the front, press on the sides of the cylinder and see if there is any movement between the frame and crane. There shouldn't be. If there is that in itself could explain a lot of things. When working with any of these older Colt's always check the crane's fit relative to the frame, and if there is a problem fix it first.

 

[Clark]

The cylinder is loose front to back and side to side.
The crane flops away from the frame when locked up.

I have another old 38 S&W Colt that looks like the same Police Positive, but the lower rod on the crane indentations for fastening is different.

There is a gun show tomorrow, and I will look to buy another one of these revolvers, that can maybe swap that part, for troubleshooting.

 

[4v50 Gary]

If the bolt isn't popping up in the double action mode, then the tail isn't falling off the shelf of the rebound lever. As you know, the bolt tail must disengage itself from the rebound lever's shelf before the bolt can pop up.

Turning to the crane, I think the crane needs stretching.

 

[Clark]

I fixed the timing since my OP.
The bolt was popping up when the hammer fell [100% cylinder movement]
Now the bolt is falling when the cylinder has moved half way [50% cylinder movement]
Kuhnhausen wants that to be 33%, but that part is working.

My problem now is that the cylinder is wobbly up and down and right to left, and the bolt is not finding the slot if the cylinder moves to fast. I have to pull the trigger slowly so the bolt will find the slot.

 

[Jim K]

Frankly, it sounds like that gun is in bad shape, either from wear or some serious damage. The cylinder should not do what you say it does, and IMHO it will be about impossible to get the gun timed in that condition. I think your first order of business is to get the cylinder wobble fixed, then deal with the timing.

Jim

 

[Clark]

I am beginning to think I am wasting everyone's time.
I would like to be a hero and fix it, but it is getting frustrating, and I could just buy a number of these and pick a good one.

I did learn how to take apart a Colt Double action and put it together quickly

 

[4v50 Gary]

Endshake is corrected by lengthening the crane. A drill rod is inserted into the crane and then the shaft of the crane is peenned and simultaneously rotated. The peenning stretches the metal and the drill rod prevents the metal from collapsing under the hammer blows.

 

[Jim K]

Hi, Gary,

I agree, but Clark says "the cylinder is wobbly up and down and right to left" which sounds like something more than endshake. I think that gun has some serious problems.

Jim

 

[Clark]

I just went to the show and looked for another Colt Police Positive 38 S&W for $100 or $150 as I have found in the past.
I saw two, one at $300 and one at $475.

I passed.

My brother paid $800 for a Python at the show. He had me carry his back pack with the Python. I kept taking it out and looking at it.

I am going to do the Kuhnhausen check list on my troubled Police Positive.
I will report back later.
Thanks to those helping.

 

[dfariswheel]

End shake is corrected by lengthening the crane. A drill rod is inserted into the crane and then the shaft of the crane is peenned and simultaneously rotated. The peenning stretches the metal and the drill rod prevents the metal from collapsing under the hammer blows

Sorry but that's absolutely not how Colt end shake is corrected.
That's one way to correct S&W end shake but doing that to a Colt will wreck it.

There's two methods Colt used to set end shake on cylinders.
The old style method from the 1900's to the 1950's has a flange on the crane. The collar on the front of the cylinder spaces on that flange. In that system it's possible to put a washer over the crane to act as a spacer between the flange and the cylinder collar.

The new style system has no flange on the crane and the cylinder collar spaces directly on the frame just below the barrel.
In this system washers can't be used.
The collar on the cylinder has to be stretched and this is done with a special hydraulic tool that "pinches" the collar and causes it to stretch.
This type of repair requires the machine, which only Colt and possibly a couple of other repair stations had.
This type of end shake repair can only be done one time due to cylinder collar cracking.
You can recognize a cylinder that's had end shake repaired by this method by the "stepped" look of the collar which has a reduced area on the front of the collar.

If you attempt a S&W repair method like stretching the crane shaft or dropping a washer into the cylinder the impact of firing will drive the cylinder bushing in the rear of the cylinder out and that will damage the cylinder, ejector, and the frame.

This is one down side of the newer Colt's that space the cylinder directly on the frame. If it develops end shake of over 0.003" it's a factory repair because no one else has the hydraulic collar stretching machine.