I did have a scope cap stick one time, and when I tried to take it off to adjust the scope the whole piece screwed out of the scope. So I know it can happen. I had to hold it with pliers to get the scope cap off. It was an old tasco that came on a used gun I got, I guess whoever put the cap on previously tightened that sucker down as tight as they could! I couldn't believe you could tighten a cap down tight enough to do that.