Originally Posted by Niles Coyote
It sounds like you are describing the size of the eye box. If that is the case all scopes will do this. Some brands/models have a wider box than others. The shadowing is cause by your eye being slightly misaligned with the scope. This can happen from the scope being mounted to high or low or shooting in awkward positions where you are not placing your cheek in the same location on the stock as you normally would.
I have many different scopes including a 6-24x50mm PST FFP MOA and love it. They all have different black rings of different thicknesses. If your eye and cheek weld is correct you should have a clear view from one edge to the other and seeing your target should become second nature.
Here is a $3,000+ March 8-80x56mm scope: