I am going with a Defiance Tenacity for my build and can only find them with the 20moa rail what scope rings/bases would I use with this setup and is it possible to sight in at 100 with a 20moa rail?
You can just use standard picatinny rings with it. Just realize that if you use a scope that is limited in its elevation travel you may bottom out before you get a 100 yard zero. If you are using any good scope this should not be a problem.