Two requisites to win a shooting match are skill and an accurate gun. Shooter skill consists of aligning the sights, following through, squeezing the trigger, etc. An accurate gun places the shots where they are aimed.
Hitting the bullseye with a .45 semiauto at 50 yards requires both skill and an accurate guna lot of luck. Even a blind squirrel can find an acorn once in while. However, to hit the bullseye 20 times for a perfect score requires a shooter with superskill using a superaccurate gun or perhaps a highly skilled shooter with an accurate gun and some luck. To date there has been neither. No entrant in a national match has ever shot a perfect score.
Therefore, we must consider these two major factors, skill and guns. What effect does each have on the score and what relationship exists between the two? There are aspects of the gun that will affect skill. Are the grips comfortable, uncomfortable, or custommade to fit the hand? Is the trigger pull smooth as butter or crunchy? Are the sights poor quality iron sights or red dot? Are the cartridges loaded down to decrease recoil, etc.? These considerations may affect some shooters and not others. Many can be overcome with practice.
The shooter, no matter how skillful, cannot control the inherent accuracy of the gun. Experimenting with different bullets, powders, primers, and cases can improve accuracy to a point of diminishing returns. After this point has been reached, the only path to better scores is to improve skill or modify or purchase a new gun.
The first step for a shooter who wants to improve is to determine what part of scoring depends on the gun and what part on the shooter. Therefore, it is necessary that the gun be tested first.
When testing the gun, the point of interest is the accuracy of the gun and its components and not the skill of the shooter. The term accuracy is some times confused with the term precision. Precision can be defined as the closeness of the shots to each other. The less distance between the shots or less variation, the more precise the shots. The closer the shots to the point of aim, the greater the accuracy of the shot.
Accurate and Precise Accurate but not Precise
Not Accurate but Precise Neither Accurate nor Precise
Fig. 10.1. The definitions of accuracy and precision.
Fig. 10.2. Group size.
The usual definition of accuracy and precision is illustrated in figure (fig. 10.1). We can interpret these figures as:
accurate and precisean accurate gun and an accurate shooter accurate but not preciseaccurate shooter but an inaccurate gun not accurate but precisean accurate gun and an accurate shooter who needs to change the sights on his gun or learn to read winds neither accurate nor preciseneither the gun nor shooter is accurate.
In tests, accuracy is generally understood as precision.
When testing for accuracy, the gun is fired a predetermined number of times at a target. The subject of interest then becomes the pattern of those shots and the group size. The group size is determined by measuring the greatest distance between any two shots in the group (fig. 10.2). This distance represents the extreme of all the shots in the group, thereby determining the amount of variation.
There is debate as to the number of shots required per group. Tests using five shot groups are the norm. However, groups of three and 10 are common. Bullseye shooters prefer 10 shot groups, aking the reasonable assumption that if the gun cannot hold 10 shots within the 10 ring, then the chance of a perfect score is nil.
Fig. 10.3.
To be meaningful, the distance between the shooter and the target must be specified. This can be 10 feet, 25 yards, 100 yards, or whatever. However, there is another method that does not consider distance. This is when the group size is given in degree minutes. A degree minute is the number of degrees measured in minutes between the end of the barrel and distance between the centertocenter distance on the target (fig. 10.3).
For example, if the greatest centertocenter distance on the target happens to be 2 inches and the distance from the gun to the target is 25 yards, the minutes of angle can be found by:
2 inches/25 yards x 3 feet x 12 inches x 60 minutes= .1333 .[MMR1]
This translates to: the tangent with the angle 7.6 minutes is equal to 0.1333. Or, the minutes of angle (MOA) = 7.6.
For example, if a gun shoots less than one MOA, the gun is shooting a group less than one inch at 100 yards This tangent can be used to find the group size at any distance. The group size at 100 yards if the minutes of angle are 7.6 can be calculated by:
0.1333 x 100 yards x 3feet x 12 inches / 60 minutes = 8 inches
The same answer can be obtained if it is known that the group size at 25 yards is 2 inches. Simply divide 100 yards by 25 yards to get 4 and then multiply by 2. The answer is 8.
This method works if the bullet spread is proportional to the distance. This assumption does not always hold true. For instance, if the test is at 25 yards the angle may increase after 50 yards and the bullets go wild at 100 yards. This is certainly true for the full Wadcutter bullet. It is best that the test be conducted at the same distance used in competition.
The method used to support the gun while firing is also important. If the gun is shot offhand in a standing position, most of the variation can be attributed to the shooter swaying and aligning the sights improperly. Unless the shooter is experienced, testing using this method is not a good idea. [MMR1]Need to eliminate space between period and formula and I cant get inside to do it.
