Gamo really poorly designed both the Bone Collector and the Fusion models. There is only the one pin stop hole in the top of the receiver. Any ordinary scope over 12.25 inches will not fit. It is designed for their el cheapo package scopes.
You have two choices.
1. Get a dove tail to picatinny offset rail adapter and a set of picatinny rings. This will allow you to still have the stop pin in the adapter and you can position the scope as you like.
2. What I do, but I have a garage full of tools and patience and knowledge from doing. I use a cobalt drill bit and drill a deeper hole in the top of the rail stop screw, I think it is call an M8. Then I file the top of the rail stop screw down even with the rail and install the ring stop pin into the top of the rail stop screw . This moves the mounts back one inch and allows the use of ordinary size scopes. This provides a new place for the stop pin allowing the assembly to move back one inch.
Kit