If you are only switching out an existing front sight and your pistol is already zeroed, simply measure your font sight height from the top of the sight to the top of the slide. (As shown in Figure 1) Use this same measurement to choose your correct sight height. If the exact size is not available, it is recommended that you use the next size higher and file the top of the front sight to reach your perfect zero.
The sight radius is the distance between the rear sight, and the front sight where the eye makes contact when referring to iron sights.
The sight radius measurement is always taken from the face of the front sight, to the back of the rear sight blade. (As shown in Figure 2)
The impact distance is the measurement of how far off your bullets are impacting, from your point of aim. If you are aiming at perfect center and your grouping is either high or low, how far off is it in inches? If you are impacting LOW you will need a SHORTER front sight. (As shown in Figure 3) If you are impacting HIGH you will need a TALLER front sight. (As shown in Figure 4)
The target distance can be based on just about any range. While 20 yards is a good distance to use, the industry standard is usually at 25 yards. The target distance will usually vary based on the pistol type (Target, Carry, and Compact Ect.) and shooters preference. The main concern is that you are shooting tight consistent groups before considering any changes to your front sight height.
IMPORTANT: When using this formula, note that all numbers are figured in inches.
Example: If your sight radius is 6.9” and you are shooting 2” low @ 25yds (900 inches) You will need to shorten your front sight by 0.015” (6.9” × 2” = 13.8” ÷ 900” = 0.015”)
If perfection is your goal, we recommend you install the rear sight and take the firearm to the range before purchasing your front sight. Whether you are just changing out just the front sight, or installing a complete sight set, you will have to know exactly where your bullet is impacting to figure for the perfect zero. You will need to have an existing front sight installed. You can try one of our recommended heights.
PRO TIP: To get the most range out of your adjustable sight, make sure the sight settings are perfectly centered. Turn the elevation screw until it stops. Now turn the other direction, count the clicks and divide by 2. This will be the perfect center of the adjustability settings. You can do the same for the windage adjustment if applicable. Next, take your pistol to the range and figure the above formula with the adjustable sight perfectly centered.