It may work for the Rugers, I don't trust it enough to advertise as such and don't offer services for Rugers if I don't own the gun and they aren't local.
The only snake gun I can think of that may have the larger frame is a 44 Mag Anaconda, never had a request to find out. The smaller Diamondback, Python, etc are more like the L-frame S&W which is 'basically' a K-frame with a full lug. In my experience the K frame fit is sloppy/loose in an L-frame holster so I do not interchange them. A lot of folks do. Lindells offers an aluminum 686 with 4" barrel which would cover 586/686/296/396/696 and any of the 45 ACP L-frame models. I'm sure I'm leaving out some, along with the Colt Python.