gun as the projected laser beam will stay true to the bore axis, and does not require removing the bolt. As laser technology has become more affordable and portable, laser boresighters have become popular for sighting in riflescopes. One type of laser boresighter is shaped like a cartridge, and when inserted into the chamber projects a laser beam through the barrel onto the target. The user then adjusts the iron sights or scope reticle to align the point of aim with the projected laser dot. Another more commonly used type of laser boresighter is attached to the muzzle of the barrel, either inserted straight into the bore ("arbor" type) or held in alignment with the barrel via a magnet, and projects a laser beam onto the target. Again, the user aligns the sights to the laser dot on the target. No matter which method of boresighting is used, the result is to align the sights to the spot where the barrel is pointing at a particular distance. Because of variations in the projectile trajectory and other factors, the boresighted rifle will always shoot below the boresighted spot and is only meant to approximate the actual points of impact, namely getting the shots "on paper" (landing in proximity to the point of aim). Live ammunition will need to be fired to further fine-tune the sighting process. Accuracy is the measure of how well the sighted object is represented. It can be measured from a specific decision-making circumstance, like the orientation of notches of a gun barrel. Alternatively, the device could be designed to accommodate a range of circumstances and still be sufficiently accurate. References Firearm components