Vector Optics VipeRay 6.5x55mm Cartridge Red Laser Bore Sight
By projecting a laser beam from the center of the barrel axis of firearm, this laser bore sight collimator allows you to instantly & accurately set your sight or scope, etc.
The laser light emitted from the laser bore tool travels in a straight line while the bullet follows a trajectory. Even though the use of this device will get you very close, final adjustment should be made at the range.