would like to get a good bore sighter without spending hundreds of $$$. Is there a decent one that will handle all calibers? Or what method do others use? I did get an old Bushnell bore sighter from a buddy's dad. has the arbors for different calibers (there's 3, although I cannot figure out how to swap them out). Nor can I figure out how to verify if the plastic housing on top (with the cross hairs for sighting) is level with respect to the horizontal once inserted into the muzzle. thanks!