Before the flat top uppers were available you had to use a carry handle mount to attach a scope. I used them for years without any major issues other than the point of impact shifting slightly when you take them off and replace them. There should be enough adjustment in the scope to zero you gun in. Some of the carry handle mounts don't tighten up correctly in the carry handle sight channel and if you grasp the scope you can wiggle them side to side slightly. It sounds like you're saying you've run out of adjustment in the red dot sight and can't get it sighted in?