My Recon came with one of those. It was cool at first, until I went to shoot it. When I slid the slide forward, the scope came off.
I noticed that the slide on the Recon has bars on it to keep such an item from sliding too far back. To fix my moving scope problem, I cut slits in the rail of it. Now it rests on these blocking bars and does not move.
Why would you use a longshot scope for anything other than looks?...
I wouldn't.