My brother is setting up his Savage 10FCP with a Bushnell ERS 3-21x50 scope. I don't have the gun or the scope and he's not familiar with scope ring height calculations. It has the factory Savage base (I think). What height rings do I need? I'm thinking 1" would be safe and 1.1" would be safer, but that's a complete guess. We are going shooting in a week, so I need to pick something and order it fairly quickly and I don't have time to get the gun and scope in hand by then. Really appreciate the help.