I had to get the EGW 20MOA base for my 93R17. It has a 4-16x40 BSA IR scope.
Initially, with the stock mounts, I had put the scope on with Redfield Medium Rings, but didn't have enough adjustment to zero the scope. After putting on the EGW base, I was able to switch to some older Weaver Low rings. The new combination leaves maybe an 1/8th of an inch between the bottom of the bell and the top of the barrel.