Last night I mounted my new Doctor red dot on my scoped grendel for close range work. It is mounted to a Burris base. I put the hard plastic cover (that came with the sight) on, and now I can't get it off! The directions say to push down and forward, but I can only get it to move about a mm, and it is on tight. This is my first time trying a Doctor, so maybe I'm missing something? Has anyone had this problem or have any ideas? Thanks.