There is no chamber length standard on a .22 revolver. The chamber length is the length of the cylinder. In the case of a rifle or single shot pistol, the chamber length is the distance from the breech to the beginning of the rifling, and does have an impact on accuracy, thus the need for a spec. I don't know whether it is still true, but I believe that S&W once used a series of three reamers to form the chambers in their revolvers. They used a roughing reamer followed by a finishing reamer, and then finally a burnishing reamer. The Burnishing reamer did not remove any metal, but just sort of ironed the surface to achieve a very smooth finish. I can remember complaints about hard extraction on Ruger revolvers when compared to S&W, and you could see the difference in the finish of the chambers between them.

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Tom
1560