In this context, the term “zero” refers to the direct correlation between the sights on a firearm and their relationship to the point of impact of the bullet. Whether the sights are iron sights, red dot sights, reflex sights, scopes, or lasers, the relationship between the sight(s) and the bore must be calibrated. This is known as establishing zero, or more commonly “zeroing” the point of aim to the point of impact at a specific distance. Point of aim and point of impact at any distance must be corrected for a variety of factors. Line of sight over line of bore, inconsistencies/deviations in mounting sights on firearms, ammunition type/bullet weight, distance to target, inclination and declination, wind drift, spin drift, the Coriolis effect, temperature and other atmospheric conditions, or the addition or subtraction of muzzle devices or suppressors, all affect shifts in point of aim vs. point of impact.