There are two adjustment screws located on the laser housing (elevation and windage). There is only one distance at which the bullet path will coincide with the laser. On a normal weapon, the sights are mounted above the bore line and are adjusted to look slightly down in relation to the bore line. When the weapon is fired, the bullet "climbs" (actually, a bullet drops from the bore line from the moment it leaves the barrel, but the bore is tilted upward slightly, so the bullet is traveling upward for a short distance), crosses the sight line, reaches its upward peak (the peak of the midrange trajectory), and descends to cross the sight line a second time. After that it's all downhill.

How the sights are adjusted, along with the muzzle velocity of the bullet (a 10mm is faster than a .45, and a rifle faster yet), determines where these points occur. The user must decide how high above or below the sight line the bullet can be allowed to strike and adjust the sights accordingly.

A laser is seldom mounted above the bore line. It is usually below or to the side. This means the bullet crosses the laser sight line only once. This point is the "zero range." For a laser mounted below the bore, at distances less than the zero range, the bullet will be above the sight line. Beyond the sight line it will be below. If mounted to the side, the bullet will also deviate to the side of the laser line, as well as up and down. The bullet will deviate from the sight line faster with a laser than with conventional sights.

In practice, an M6 on a handgun can be adjusted to keep the bullet strike within about 2" high and 2" low out to about 100 feet, which is better than most people, and a lot of guns, can shoot.