Scope alignment tools, more commonly referred to as boresighters, gives shooters the opportunity to sight in their rifles without having to fire it. Scope alignment tools provide a reference to the rifle's projected point of impact -- where the bullet will hit -- to which the scope can be adjusted. Boresighters use the rifle barrel to determine the point of impact.
Optical boresighters attach to the end of the barrel and present a grid which can be seen by looking through the scope. By adjusting the scope's crosshairs to the center of the grid, the scope aligns with the barrel.
Bullet Shaped Laser Boresighter
This laser boresighter is shaped like a bullet and is placed directly into the rifles action, closing the action activates the laser which sends a beam through the barrel to the projected point of impact. The shooter then looks through the scope and adjusts the crosshairs to intersect on the laser beam. The limitation of this type of boresighter is that can only be used with the caliber that the boresighter is based on.
End-Mounted Laser Boresighter
This laser boresighter operates in a similar fashion to the bullet shaped laser boresighter, in that the laser projects a beam to the point of impact. However, this laser is mounted on the end of the barrel. An advantage of this type of laser is that it can accommodate a variety of calibers from .22 to .50.