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[1] [2] On the other hand, the grouping displacement (the distance between the calculated group center and the intended point of aim) is a measure of accuracy. Tightness of shot groupings are calculated by measuring the maximum distance between any two bullet holes on the target (center-to-center) in length measurements such as millimeters or ...
Example of a ballistic table for a given 7.62×51mm NATO load. Bullet drop and wind drift are shown both in mrad and MOA.. A ballistic table or ballistic chart, also known as the data of previous engagements (DOPE) chart, is a reference data chart used in long-range shooting to predict the trajectory of a projectile and compensate for physical effects of gravity and wind drift, in order to ...
whose solution is known as Beer–Lambert law and has the form = /, where x is the distance traveled by the beam through the target, and I 0 is the beam intensity before it entered the target; ℓ is called the mean free path because it equals the mean distance traveled by a beam particle before being stopped.
At 2,400 m (2,625 yd) the total drop predictions deviate 47.5 cm (19.7 in) or 0.20 mil (0.68 moa) at 50° latitude and up to 2,700 m (2,953 yd) the total drop predictions are within 0.30 mil (1 moa) at 50° latitude. The 2016 Lapua Ballistics 6 DoF App version predictions were even closer to the Doppler radar test predictions.
It is especially popular as a unit of measurement with shooters familiar with the imperial measurement system because 1 MOA subtends a circle with a diameter of 1.047 inches (which is often rounded to just 1 inch) at 100 yards (2.66 cm at 91 m or 2.908 cm at 100 m), a traditional distance on American target ranges.
The first equation shows that, after one second, an object will have fallen a distance of 1/2 × 9.8 × 1 2 = 4.9 m. After two seconds it will have fallen 1/2 × 9.8 × 2 2 = 19.6 m; and so on. On the other hand, the penultimate equation becomes grossly inaccurate at great distances.
Similarly, an adjustment click on a scope with 0.2 mrad adjustment will move the point of bullet impact 2 cm at 100 m and 4 cm at 200 m, etc. When using a scope with both mrad adjustment and a reticle with mrad markings (called a mrad/mrad scope), the shooter can spot his own bullet impact and easily correct the sight if needed.
For reference a 1 MOA circle at 100 yd (91 m) has a diameter of 1.047 in (2.7 cm), 3 in (7.6 cm) at 100 yd (91 m) equals 2.9 MOA, and 5 in (12.7 cm) at 100 yd (91 m) equals 4.8 MOA In summary the accuracy standards of the Gewehr 98 and most other service rifles used in World War I and later were similar.