Want to confirm your Bore… a 7/32“ drill bit will fit and slide in a Bore that will handle both 22lr/22WMR.
IF the bore is 22lr only, it will not fit.
Suggestion; use the BUTT end of the drill bit, .
The 6.5” Bisley 22lr introduced ~1984/85 were not built as convertible’s, however I have successfully added a WMR cylinder and the gun really likes it. Notably more accurate vs the 22lr.
Here is a thread (way back) that might be of interest to you. At this time I had a stainless MAG cylinder, Now I have a blued cylinder.
I have seen on Ruger's website that they will "fit" a .22 Mag cylinder to a Single Six. What is involved in this, as I've seen cylinders for sale. Is each "fitting" unique to that given revolver, or will any .22 mag cylinder work in any single six? Rookie question I know, but thinking of...www.rugerforum.com