You should be able to drill away the screw head with a bit slightly larger than the shank of the screw and lift the top of the ring off. After the ring top is gone the stub of screw should be still sticking up and if it wasn't loctited in easily removed with a needle nose or if loctited, heat it and remove with pin vise or locking pliers if you want to save the rings.

After the first shot the rest are just noise.