if you decide to remove the screws via drill. use a bit just large enough to completely take the head off when it gets to the shank of the screw. pull the base then the screws should come out easily, unless of course they were cross threaded on the way in.i think eddies hiding it under the front mount, the screws for the mount were sure tight being on for 40 years or so i starting to strip the heads even heating them up with a propane torch so i would have to drill them out screwing up the mount threads in the process, to much work too see them i gave up the base was flat and level perfect to mount a rail job on it so i just did it