Shot grouping
In shooting, a shot grouping, or simply grouping, is the placement of multiple shots on a target, the shots taken in one shooting session. The closeness of the grouping, the nearness of all the shots to each other, is a measure of the accuracy of a weapon, and a measure of the shooter's consistency and skill.[1][2]
Uses of the term
For firearms that shoot one round at a time, a shot grouping test can be used to measure the accuracy of the shooting system: the weapon's mechanical precision and the uniformity of the ammunition. The weapon is fixed into position on a test mount, and aimed at a target. Multiple shots using rounds from the same type and batch are fired to observe how the weapon groups the shots. If a person holds the weapon and shoots it, the grouping measures the combination of the person's skill and the weapon's accuracy.[2]
In shotgun shooting, the grouping is also called the pattern. The pattern is the spread of shot from a single shotgun shell, measured as the smallest circle containing all the shots on the target. The barrel of a shotgun is designed to deliver a wide or narrow grouping, depending on the expected use. Shooting at close range indicates a cylinder bore barrel to deliver a wide grouping, while for hunting at longer distances such as 50 yards or meters, a choke is recommended for a tighter grouping.[3]
In archery, a shot grouping is the result of one person shooting multiple arrows at a target. A tight grouping indicates consistency in form.[4]
Firearms
Shooting accuracy is measured in minutes of angle (MOA). When shooting at a target 100 yards away, one MOA is a circle 1.047 inches in diameter, while at 100 meters, one MOA is a 29.1-millimeter circle. The MOA is an arc-based measurement, with one MOA equal to one minute of one degree. The two-dimensional circle surrounding a shooter always has 21,600 MOAs because there are 60 minutes in each degree, and 360 degrees in the circle. A big-game hunting rifle is considered accurate if its shots fall within 1.5 MOA, while a rifle intended for small animals is expected to have an accuracy of one MOA or less.[1] Handguns are typically less accurate; at a shooting distance of 25 yd (23 m), a grouping is considered acceptable for self-defense if the shots fall within a circle of 4 to 5 in (100 to 130 mm), which is 15 to 19 MOAs.[5] Expensive and well-machined match-grade pistols demonstrate a higher accuracy than normal handguns, capable of groupings of 1.25 in (32 mm) at 25 yards, which is between 4 and 5 MOAs.[6]
Mean point of impact (MPI) is the calculated center of the grouping, which is the average center of all the shots, and is not necessarily located at a hole in the target.[2] The size of the grouping is described as the smallest circle containing all the shots.[7]
A "flier" is a shot from the same shooting session that is farther from the general shot group, considered to be outside of the grouping. Such shots may be the result of an unexpected gust of wind, a muscular flinch of the person shooting, or it may indicate a problem with the firearm mechanism. Rarely, it may indicate inconsistency in the ammunition.[8] Single fliers may be discounted when evaluating a grouping, but if fliers occur often, then the problem should be traced to its origin.[2]
While target shooting with a handgun, if a grouping is consistently off-center then the shooter is instructed to alter the body angle or the stance, rather than shifting the arm, wrist or hand, which should remain in position.[9]
Archery
With the increased element of human skill in archery, a grouping on target is more a measure of the archer's skill. If an archer is not getting a consistent grouping, then their basic form needs work. If an archer's arrows are grouping on target but off center, this shows consistent basic form, with better results achievable after slight adjustments.[4][10]
On the equipment side, bow stabilizers have been used since the 1960s by tournament competitors and by bow hunters to counteract the torque of shooting the arrow. A tighter grouping may be achieved with such a stabilizer, which adds mass extending outward on a moment arm, usually mounted perpendicular to the bow riser, aligned with the arrow path.[11][12][13]
Example groupings
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Handgun and paper target showing grouping of ten shots
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Offhandgroup25.jpg
A grouping made with a five-shot revolver
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Paper Target.jpg
Eight-shot grouping
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Glock31 220510.jpg
Multiple shots from a semi-automatic handgun
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Archery practice.jpeg
Arrow grouping with fairly consistent results but slightly off center
References
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- ↑ Haywood and Lewis 2013, p. 15.
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