Re: End-shake
There are two methods.
The FACTORY method, which is the only one really approved, is the collar swaging/stretch method.
In this method a hardened steel support "spud" is inserted into the center of the cylinder where the crane fits.
A special hydraulic "jaw" device is fitted over the collar on the front of the cylinder and the device "pinches" or compresses the collar.
The cylinder is rotated and squeezed until there is a reduced "step" on the entire diameter of the front of the collar.
This produces a reduced diameter on the front of the collar which is how previously stretched collars are identified.
Then, the now longer collar is refit by using a milling machine to trim it to length.
This is a ONE TIME fix for cylinder end-shake, since the collar work-hardens and reduces the thickness the collar, a second attempt will crack it.
Also, due to the short length of the collar, it's not possible to get a second "bite" on the collar with the tool jaws.
The second, non-factory method is used as a restoration method on guns in which the collar can't be stretched for some reason, and the original cylinder needs to be retained.
In this method a lathe or milling machine is used to bore out the front of the cylinder to a larger diameter, removing the collar in the process.
A hardened steel bushing is made up and press-fitted to the larger hole.
This is then trimmed to length with the mill.
In this method, the new collar bushing is fairly short, and is similar to the pressed-in collar's used on S&W revolvers.
In these other guns, the bushing collar is nothing more than a bearing for the crane or yoke, since these guns don't space on the collar like the Colt's do.
This method works very well, and the bushing can be replaced if further end-shake appears.
The only requirement is the boring MUST be done in a highly precise, very exact way and based on the inner diameter of the original collar, NOT on cylinder diameter.
This is due to the fact that dead-center of the cylinder is based on the inner surface of the collar, NOT on cylinder diameter.
The factory-approved collar swaging method is done by both Colt, and at Pittsburgh Handgun Headquarters.
The other is best done by an absolutely crack pistolsmith/machinist who's had experience at doing the job.
In general, the first choice is a cylinder collar stretch, due to the lower cost of having it done.
The bushing method should be reserved for guns that have already been stretched, for cylinders that have damaged collars, or collars too short to be stretched beyond the .006 to .008 maximum stretch limit.
Because of the cost and difficulty in finding a QUALIFIED 'smith to do a bushing job, the stretch method is preferred for guns that can be stretched.
Due to the Colt design, it's not possible to do a simpler yoke tube stretch or washer job like on the S&W.