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Sight Radius Calculator, Effect on Accuracy Explained & How Range Time Improves Shooting Skills

Sight radius is the distance from the rear of the front sight to the rear of the rear sight. The longer the sight radius the more accurate you will be. There are many explanations for this, but two most quoted examples are that sight deflection is minimized with a longer sighting radius. Some also maintain that the longer barrel gives a longer time to stabilize the bullet.

Iron Sighted Rifles Are More Accurate with a Longer Sight Radius

You are moving the barrel through an arc to align your sites. The center of the arc is the rear sights. Many military rifles have a post or blade front sight with an aperture or peep site in the rears. Again, given the same caliber, iron sighted rifles will be more accurate with a longer sight radius. A 16” .243 will not be as accurate as a 22” barreled .243 all other things being equal. Take two protractors a 4” diameter and an 8” diameter. On the smaller one the degree markings are bunched, and perhaps each mark counts two degrees verses the larger 8” with perhaps marking every ½ degree, far more precise. The same accounts for longer sighting radius and the ability to dampen out the movements and lessen the deflection.

Sight Radius Calculator


As noted above, a mere half a millimeter on a 3” sight radius produces a sighting error of almost 3” at 25 yards, while a Thompson/Contender with nearly a 15” sight radius is only off about 6/10th of a inch at the same range. Trig was used to discover the SIN, giving our deflection in degrees. All calculations where done in degrees and millimeters, with the deflection at 25 yards converted to inches. The formula was TAN θ x distance will give you the calculated deflection at 25 yards. 25 yards equals 22,280 millimeters. A ½ millimeter is only about 2/100th of an inch and is minor, but any error is multiplied by a shorter radius. Given the tunnel vision and loss of fine motor control it is little wonder that two untrained shooters can stand 4 feet apart and empty their weapons without a hit on each other, well the case cited included a highly inebriated state of both shooters. The community at large was in more danger than the participants. The building took some hits as well.

Range Time Improves Shooting Accuracy Through Practice & Training

The mantra sight alignment and trigger control are illustrated by the compounding of error over a short sighting radius. Therefore, range time contributes to accuracy through practice. Double action shooting is affected more than single action revolvers or semi-autos. There is a tendency to pull towards the trigger finger if shooting double action. The only way to overcome this is through practice. Trigger control between double action and single action are so varied that is why many semiautos, like the Glocks are double action only. On DA-SA semiauto where the first shot is double action, the impact point tends to shift left in single action shooting. Many though shoot better with a 6inch barrel than an 8 ¾ inch barrel, as they are muzzle heavy, so longer is not necessarily better for some. Those with the strength or if you can shoot from a rest will do better with the longer barrel with iron sights. Shooting Range Industries offers custom designed shooting ranges. Contact us to learn more today!