Well, where to start?
First, this sort of post will get more attention in the gunsmithing section.
Second, your concept of what an endshake bearing can do is rather different from their actual function. An endshake bearing reduces endshake but does not "tighen up the gap." When you hold the cylinder all the way to the rear, that's about where it will be after endshake is corrected. A B/C gap of up to .010 is considered within S&W tolerances, and reducing it is neither simple nor cheap: the barrel has to be set back.
Third, the yolk endshake should be checked and corrected before tackling the cylinder endshake.

This is a good book for understanding how a S&W revolver fits and functions.
"The S&W Revolver: A Shop Manual" Book by Jerry Kuhnhausen - MidwayUSA