Originally Posted by Len Backus
How far rearward should I mount the scope's ocular bell knowing that this is a rifle scope on a handgun?
There are many ways to hold a handgun. There are many variations on handgun grip position relative to the receiver and scope mounts. Different people have different ability to control a handgun's recoil. That and the geometry of the handgun determine how much the scope will move on recoil.
Bottom line is a scope needs to be mounted far enough forward it won't cut your skull when fired and far enough back your eye is at or near the scope's exit pupil. If those overlap you'll need a scope with longer eye relief or a better muzzle brake.