"ls308"
The front "bell" of many scopes have what is called an adjustable objective.
It is a very necessary device for scopes over about 10X magnification. It is usually marked with ranges like, 50, 75,100,150,300 yds and finally infinity. You turn it to the yardage at which you are shooting to insure a clearly focused sight picture with as little parallex as possible. What I meant about being sensitive was that the Alpen requires adjustment or focusing a bit more than some of my other scopes. That is not necessarily bad, especially if it works. On mine, if the target is a little out of focus a small twist on the objective ring will quickly bring it into focus. In theory, it could be used as a "poor-man's" rangefinder, however, I haven't seen any scopes with adjustable objectives or parallex adjustment devices that are sensitive enough to do that! Hope this all helps rather than muddying up the water more!
Good luck,
Jim