CJ Davis demonstrates the Nikon Bolt XR Crossbow Scope at the 2011 ATA Trade Show
The Bolt XR scope was designed specifically for crossbows. It is a shorter Scope to fit the mounting platform of most crossbows and this particular scope has a BDC 60 Redicle inside that gives you aiming points so if you sight the crossbow in at 20 yards you have an aiming point for 30, 40, 50 and 60 yards. Nikon BDC's are all built around small circles that allow the crossbow hunter to center the crossbow like you would the peep site of a compound bow.
The Bolt XR is built based on a 305 feet per second crossbow but if you have more speed then that with your crossbow shortly you will be able to go to the spot on software on the Nikon Hunting website and put in your velocity and the software will tell you exactly where the circles in the scope are going to hit for you at that range.