On Friday, May 31st, discover more about the UFO phenomenon than ever before in a six-part docuseries that goes inside the Pentagon’s research on the unexplained. Watch “Unidentified: Inside America’s UFO Investigation” on History. | HISTORY

In part 4 of our 4-part series on how to properly mount your rifle's scope, Ryan Cleckner, former Army Ranger sniper team leader and author of the Long-Range Shooting Handbook, discusses how to troubleshoot some potential issues when mounting a scope to a rifle. If you're looking for scope mounting components that fit your rifle check out Gun University's free scope ring finder tool here: https://gununiversity.com/scope-ring-finder/. Check out Ryan's book Long Range Shooting Handbook: A Beginner