Don't know anything about scope rings, not sure if there is a standard.
Also since these RAR come with built in rails not sure if there is a type of ring that can fit on, the rings I have searched say they fit on "weaver" rails, but searching the ruger website it doesn't say it these are "weaver" style or not.
That brings me to hight, is it just a preference if not why make low/medium/high rings? What is most commonly used on the RAR?
If this is covered somewhere else please post link, don't have computer only tiny tablet, very difficult to search.
Thanks

 

I have lots of experience mounting scopes of all sizes to a bunch of different American rifles.
The weaver style rings are what you need for the Ranch rifle and the standard American rifles. On the Predator, you can use either weaver or picatinny. As far as height goes, a 3-9x40 needs medium rings (Weaver brand or Warne brand are the only two I've tried, so other brand "medium" rings might be slightly higher or lower). On longer scopes (12 or 14 or greater power) where the objective lens is further forward and over the thinner part of the barrel, you can get by with low rings for 40 mm scopes.

 

Thanks so much for your help, wasn't sure after 93 views if it was going to get answered. Haha